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

Maybe. But this is where Canon wins. It's not worthy of upgrade from D90 to D5100 if you have a huge arsenal of AF lens. D7000 will be a more appropriate choice then. It's true that most amateurs who buy D5x00 or D3x00 will be satisfied with the kit lens. But more serious enthusiasts will find the lack of the motor quite appalling. The fast prime AF-D lens won't be of any use(well, that's exaggerating. We can still use them with MF), and their AF-S counterparts are quite expensive for poor boys like me.