I use the MS-BRIT SILVER model. To me it just sounds more real than most of the other ones.
I set the amp drive on about 5, and I use the "Screamer" to get the gain up there.
I use the 4x12 treadplate for fooling around, but if I'm going to record something I really want to keep, I'll use impulses. They sounds worlds better.
Oh, and I also roll off a lot of high end with the on board EQ. I think the top end of everything the POD does sounds like cock and balls.