D5000 over the the t1i..
the t1i was never a good step even over the XSi really.. never sold really well for that reason..
however, now the t2i is out, which is an AMAZING camera...
as to lenses...
if you look directly at Cannon or Nikon lenses, Nikon is almost more expensive every time..
Cannon does a significantly better job of "mid grade" non professional level lenses and prices... however they also have their L series which is as good if not better than the nikon lenses in most cases... but you pay for it...
That said, at the end of the day, non oem lenses are out there for both camera's which are USUALLY cheaper (or more expensive) than either cannon or nikon specific brand.. there are some negatives with the non oem lens, but those have to be investigated on a case by case basis...
Cannon again IMHO tends to be at the front of the non oem brand lens game... tending towards cheaper, and more selection....
IMHO, if i was buying a mid range SLR right now.... the Cannon T2i not the t1i would be my purchase..