Laggy - you try to open and app, file, answer the phone, etc.. and the phone is less than responsive. I've got a touch pro right here at my desk and my E71 runs circles around it when opening a word doc and editing it. How sad is that?
HTC already puts pretty large batteries in their phones. My touch pro has a 1300 mah battery in it. By comparison, my n85 has a 1200 mah battery in it, yet, my N85 will do more and last much longer. The problem isn't the size of the battery, it's the resource-hogging OS that is WM. Of course, needing to run the touch-flo UI band-aid doesn't help, either.
I guess HTC could drop a 2400 mah battery in its devices, but, then they'd be 3 inches thick. lol