I am still of course an immense Vernor Vinge fan, but new Vinge books are few and far between, so I'm reluctant to name him. Charlie Stross, well, I really like him but he's highly eclectic. With every book he tends to hare off in a different direction: he'll do a space opera, then a Mundane SF book, then a fantasy brickology, then a Heinlein pastiche. All his books are quality but they aren't always things that totally push my buttons. And I would have called Jack McDevitt my number one at certain points, but he's become kind of the anti-Stross, playing it safe with low-key sequels the last several years, so I can't honestly keep him in that slot either.
Reynolds, though, pretty much always works in my favorite genre (New Space Opera, which you might sum up as classic space opera mixed with cyberpunk) yet, while he does have his Revelation Space universe he works in, he mixes them with books that have entirely original settings (Century Rain, Pushing Ice, et cetera.) Plus he's quite prolific but still manages to keep the quality level up. I don't like everything he's written -- I found the original Revelation Space trilogy too dense to enjoy -- but I've liked enough of them that he's hit my "buy on sight" list. Soon enough, House of Suns, another original universe! I'm seriously anticipating that one.
So what author's books are you looking forward to the most right now?