I've played that. It's hypermodern and gives Black a lot of latitude but does require Black to think, as most players are not well-booked on the 1.b3.
unusal openings everyome is suprised when you play it

Modern Benoni! I've played it twice in Live Chess and each time it gave my opponents about 45 seconds of pause to figure out what the heck it is.
(unfortunately, I'm awful in Live and lost both games, but they were going really well until I blundered!)

You don't feel that white has more than sufficient compensation for the doubled pawn because of the weak black squares after ...0-0, especially holding the bishop pair and with the queens still on? As you say, blacks progress into the apparently open queenside is often strangely awkward in positions like this, particularly as white is like to play actively on the kingside immediately.
Or is the idea to hold out for ...0-0-0? If not, how are you meeting f5 ideas?
EDIT - but perhaps this is what you meant by nuts but fun!

A move like ...Bxc3 would be better if the bishop wasn't on g7 first. It looks like the kingside king would be too weak while if black actually wanted to castle queenside it would probably take too long. And that g7 bishop was extremely strong.

Precisely. And everyone is certainly surprised by it, like the title said (it's good for blitz).
Yes, I was going to say that I certainly would be surprised to see an NM choose this line!
And actually, black can dig in pretty deep on the queenside for a cheap time win, assuming your opponent already spend a minute and a half wondering what the hell you were doing...
I play the larsons(b3)