I have played 1. b3 quite a bit over the last two years (on turn-based sites).
I like it alot and never mind seeing 1. ...e5-- there are other set-ups for Black that are more annoying than 1. ...e5! Also, the King's Indian is fun to play against because of the different options available, such as 1. b3 Nf6 2. Bb2 g6 3. Bf6 and then a later c4 to clamp down on the d5 square. Not too scary for your opponent to face-- just a completely different middlegame position to be played.
I kind of dread playing Black against any set-up that has a bishop at b2 because you have to be alert at ll times to the fact that bishop is bearing down on your kingside and trying to control the d4 and e5 squares.
I wish I could play 1. f4 d5 2. b3 without all the other variations being available to my opponent, but that's just not realistic! I guess I could transpose with 1. b3 d5 2. f4 and be happy with that!
Oh, and the Nimzo-Larsen Attack book by Jacobs and Tait is great! And necessary!
I play 1. f4, but often I find that Black can play 1...g6, "preventing" 2. b3, a pretty strong setup for Bird's Opening. So the debate could be shifted this way...
Why not play 1. b3? One obvious downside for a Bird's Opening player like me is that Black can immediately play ...e5. However, White still has a flexible position - he can still enter into an English 2. b3 system, or even play 2. e3 venturing into reversed Queen's Indian territory, or even preparing a slow d2-d4, or playing a double fianchetto and assaulting the center with a reversed Hippo.
Obviously, this very flexible choice is worth debate. It may not be one of the top choices, but White definetely has not "handed the cards" to Black.
So, has anyone had any experience with this opening, good or bad?
My closest experiences with it is actually from the Black side, Owen's Defense, which I intend to start a blog on shortly. I believe that any player of the Nimzo-Larsen, 1. b3, ought to also consider Owen's Defense.