A very solid backup. Mine served me well for a couple of years, although I literally had not touched it since I upgraded to my Atrix last May.
Today the Atrix battery has crapped out on me. Still not taking any charge even after being on a charger all last night, all day at work, and since I've been home. I'll probably need to replace it, but when I got home tonight, I found my good 'ole G1 in a drawer of abandoned phones.
Even after sitting idle for over a year, it still powered on immediately, and is running like a champ. As great as the Atrix has been, I still miss this phone on occasion. I'm kind of looking forward to playing around with this one again for a few days.