I've decided to take up thene's challenge, but I'm going to cheat, because the male sci-fi writer I'll be testing is Isaac Asimov. This is cheating because it's clear from the context of her post that thene is talking about current male sci-fi writers. Nevertheless, Asimov it is, for two reasons. One, he's the sci-fi writer whose works I'm most deeply versed in; and, two, I think he'll serve as a sort of baseline writer.
The test itself is pretty easy, since, as I cast my mind over Asimov's body of work, I honestly can't think of any sex workers among his female characters, giving him a rating of .000 on the Miller Scale. I suspect that thene might consider this too much of a good thing.
The reason for Asimov's low score isn't hard to work out. He was a product of the pulp SF tradition of the 1930s, and he first gained fame in the pages of the Golden Age Astounding Science Fiction, quite possibly the most puritanical SF magazine of all time. A lot of his stories didn't have any female characters, and the few who did appear tended to be wives and girlfriends (though there were a couple of very notable exceptions). And unlike some of his fellow Campbell Authors who continued writing into the latter part of the century, Asimov didn't take advantage of the freedom from censorship to explore sexual themes. His writing remained just as puritanical as it had been in the 1940s.
It wasn't until his fifth story, "Ring Around the Sun", that Asimov even created a female character:
Jimmy Turner was humming merrily, if a bit raucously, when he entered the reception room.
"Is Old Sourpuss in?" he asked, accompanying the question with a wink at which the pretty secretary blushed gratefully.
"He is; and waiting for you." She motioned him towards the door on which was written in fat, black letters, "Frank McCutcheon, General Manager, United Space Mail."
And that's it, Isaac Asimov's first female character, a nameless secretary who is described simply as "pretty" and who is grateful to be winked at. His next couple of female characters are equally minor: an industrialist's wife in "The Magnificent Possession" and a wealthy starship passenger in "Black Friar of the Flame". However, in his fourteenth story, "Robbie", Asimov finally has a major female character: Grace Weston, a shrewish housewife. Grace takes a deep dislike to her eight-year-old daugher's robot nursemaid and nags her husband incessantly until he agrees to send the robot back to its factory.
It wasn't until his 28th story, "Liar!", that Asimov created a female character who wasn't some other character's wife, girlfriend, or secretary. This was Dr. Susan Calvin, a robopsychologist at the United States Robot corporation. Although she would later gain in stature, in this first story Dr. Calvin's role was an inglorious one: she was a plain, bespectacled, spinsterish woman in her late 30s with an unrequited crush on a handsome male co-worker several years her junior. In later stories such as "Escape" and "Little Lost Robot" she took on her defining characteristics: her icy demeanor, formidable intelligence, and disinclination to suffer fools gladly.
It was in 1945 that Asimov created his first fully rounded female character (or at any rate, as fully rounded as his characters ever got) in his short novel "The Mule": Bayta Darrell, a historian and member of the democratic underground on her despotically ruled homeworld. "The Mule" reaches its climax when Bayta kills a man in cold blood to keep him from revealing the most important secret in the galaxy. Yet, Bayta is also a housewife who as a matter of course cooks and cleans for her husband. Asimov had been married for three years when he wrote "The Mule", and he based Bayta on his own wife.
Asimov followed up with "And Now You Don't" in 1949, a story featuring Bayta's granddaughter, Arcadia Darrell, a 14-year-old schoolgirl and aspiring novelist with a romantic streak. "And Now You Don't" also featured a second prominent female character, Lady Callia, who is apparently the scatterbrained mistress of the Warlord of Kalgan, but is actually a secret agent from a group of highly advanced mental supermen.
In the Empire novels of the early 1950s, the few female characters served mainly as a love interst for the male heroes. In the two robot novels of the mid-1950s, all the female characters served mainly to move the murder mystery plot along (though admittedly, so did all the male characters except Baley and Daneel). By contrast, in 1955's The End of Eternity, the character of Noÿs Lambent is actually the puppetmaster pulling all the strings from behind the scenes -- as well as being the hero's love interest.
There followed a period of a decade and a half when Asimov concentrated on writing nonfiction. This ended spectacularly with his 1972 novel The Gods Themselves. The first section, in an echo of his Astounding days, had no female characters; the second section had no human characters at all; but the third section had an actual female viewpoint character, a Lunar tour guide named Selene Lindstrom. Selene is pretty much the opposite of the standard pulp fiction female character: independent, intelligent, outspoken, and thoroughly in control of events.
Ten years later Asimov published Foundation's Edge, his first work in that series in over thirty years. Conscious now about the lack of female characters in his earlier stories, he made an effort to even the sexual balance in Foundation's Edge, and the result was four major female characters: the Thatcheresque Mayor Harla Branno, the power-hungry Second Foundationer Delora Delarmi, the Trantorian farm girl Sura Novi, and the Gaian Blissenobiarella.
Women continued to play prominent parts in Asimov's fiction, most notably the artist and fashion designer Gladia Solaria in The Robots of Dawn and Robots and Empire, Blissenobiarella in Foundation and Earth, the telepathic teenager Marlene Insigna Fisher in Nemesis, and the historian Dors Venabili in Prelude to Foundation and Forward the Foundation (though, being an android, Dors probably doesn't count).
So, how does Asimov do in the Frank Miller test? He was a pulp writer who, in his later years, consciously sought to overcome his pulp origins to create female characters who were the intellectual equals (for good and ill) of his male characters.
UPDATE: Thene responds in comments by pointing to the Bechdel Test as a better determinant of whether a piece of fiction can be considered feminist. The three basic requirement of the test are that a work of fiction:
1. Has to have at least two women in it,
2. Who talk to each other,
3. about something besides a man.
Failure to meet the Rule is a strong indication that female characters are under-characterized or under-developed in the work.
ISTM that the Bechdel Test would be more applicable to mainstream fiction than genre fiction, since mainstream fiction tends to be more focused on (and have conversations involving interpersonal relationships, while genre fiction is more likely to involve conversations involving a genre-specific situation. Provided there are a sufficient number of female characters, there's a pretty good chance that at some point, two of them are going to talk about How do we get past these zombies? or Does the butler's alibi hold up? or Is it safe to land on this planet?, thus technically passing the Bechdel Test despite the presence of under-characterized or under-developed female characters.