"My question is how does Blue3 compare to NI's B4-II? "
Well, I guess to answer my own question, I downloaded the demo and went through all the rock presets (having spent just a few minutes with each) I think it definitely is a contender. I did a side by side comparison to the B4-II
and it sounds like it has a little more punch. The Leslie speaker sim is pretty good too.
I agree that some of the presets do sound a bit "synthy" as someone commented, but many of the other presets sound very natural. It's a tough call. But for $99, you can't really complain. I'm thinking when payday rolls around I might just get it.