Interesting you have that issue. I keep mine in my pocket all of the time, and NEVER have it turn on. The only time it has happened is when I hold a kid that bumps the phone. Besides that, i've never used a lock program. For the Treo I did cause that would turn on here and there.
Now I bet kids who wear skinny pants have the issue all the time cause the phone will barely fit in the pocket and the slightest move of the leg probably turns it on.
If you have skinny kid pants....