I have a T21 for 2 yrs and 8 mos now. The battery died compeltely a few month ago. now it's on AC full time. The unit is very solid though, dropped it once to hardwood floor from coffee table, nothing happened. Another problem: it now runs at 650Mhz instead of 800Mhz after battery is taken out. I believe this is a design flaw. I disabled the "intel speedstep" and it's supposed to run at 800Mhz at all times.