Does anyone here use it regularly?
No, but I regularly have to debug/clean up what it produces
what do you think of it?
Best left unsaid, I think.
any tips warnings etc?
Learn HTML. Not rocket science by any stretch. Take you a day or so
FP is OK for those who just want a quick homepage. If you're going to be doing any serious site work you will end up with fat, inefficient code and unnecessarily large pages. And if you intend to do any server-side scripting, FP will more often than not scr*w it up for you. YMMV of course.