Its horses for courses Alex, so they tell me. I have a friend who just bought a Hasselblad H1Digital set up - and he has no pretentions to be a pro whatsoever!
If you look through the forums on sites like Rob Galbraith, you'll see that many Stock agencies are insisting on 10MPixel+ cameras being used. This is of course because the quality is far superior and has absolutely nothing to do with not wanting to get swamped with too many images to handle whatsoever. Of course they must have files from high MPixel cameras, it stands to reason.
I figure myself that good images will out, but during a recent image collation project I have been involved in I discovered another variation on the nmatural law of difficultness. This states that the better the image in terms of its content, lighting, composition, etc., the lower the MPixel camera it was shot on!
One good thing about today's 10MPixel+ cameras is that they'll be a lot cheaper in a year or so and still very, very good. Bit off topic but there you go.