Choosing between Nikon D5100 and D90.. Any help greatly appreciated!

Thank you for your response, it's a pretty tough decision that I really don't want to regret!

I just have a slight feeling that the D5100 won't last me, and I'll be looking for more from the body in terms of ergonomics.

But with the D90, I'm worried about the single lens/older sensor.

AH! Maybe I'm looking into this too much. I need to just make a decision and stick to it. I'm sure I'll be very happy with either decision.