I've got going on 3 years experience with Hammer now so if you need any help I can assist, although I haven't tried any TF2 mapping yet.
Interlopers.net - Half-Life 2 News & Tutorials is your best bet for learning all things hammer related though.
The editor itself is very friendly both in usage and of course the fact that help is always easy to find. It hasn't had any major changes since it's conception, though (actually it hasn't had many big changes since it was called Worldcraft, really). The style has always been the most intuitive to me however, but it may suck coming back to it from a UE editor since yeah, the way you construct maps is basically backwards (although BSP makes way more sense to me than CSG).
