I carry mine in my pocket all the time with nothing but a screen protector. Sometimes the trackball gets a little funny but RIM's fix works every time. However, I do have my phone's keys locked. It is not uncomfortable in my pocket at all. Unlike my first phone (Motorola V330) which was almost an inch think. :-/
PS: RIM's fix it pushing in the trackball and rolling it in the direction it does not want to go.