There is a proximity sensor app in the market place that people recommend; I have never personally used it because I don't have the face mashing problem.
I am moving to the Droid soon from my Hero. Not that I don't like the Hero, I think it's a fantastic device. I find the keyboard to be one of the best SIP's on the market and it's auto correction is fantastic. Lag wise I have some from time to time but nothing like a Win Mo device. However it does seem to be getting worse; I am probably at the point now that I need to clear some cache and uninstall some programs. All and all I am fairly happy with the responsiveness of the device. I often listen to two plus hours of podscasts/music while browsing/texting/installing apps/ or writing on forums; I get some slow down but it's fairly minimal though at times it gets super annoying.
My move to the droid is both exciting and a tad worrisome. I am excited for the bigger screen, hardware keyboard and better hardware specs. I am hoping that when listening to podcasts the device will not be as laggy as the Hero is. I am hoping that I will be able to push the device a little bit farther then I can with the Hero. Since I will finally have 3G with Verizon that will help a lot. However I am worried about the on screen keyboard not living up to the Hero's frankly I don't want to have to spend money for a keyboard. I worry a little bit about the hardware keyboard too it doesn't seem to be the greatest one ever made. I am worried that the device might not fit as well into my life has the Hero has.
I've had a ridiculously large # of pda/smartphone/media devices and the Hero is honestly the first device I use for everything. So I hope that the droid is able to play and improve on that same role. Sadly I wont find out till Wednesday, and I work and have school all that day so I won't have much time to play