My N900 is still my daily use phone and its still going great even after accidents (falling out of my bag onto the floor for example) that would have rendered lesser phones *cough*iPhone*cough*Galaxy*cough* dead.

I do have a bunch of cosmetic issues but the only the only thing that has actually failed was the USB port but I was able to get that sorted.
Oh and I think I am on my third battery after the original Nokia and the first replacement both stopped holding a charge.

No I dont have a backup phone for dev purposes, I run all my dev stuff on my daily-use phone (including things like my MCE clone)