I've pre-ordered it for the PC, I very rarely pre-order these days as most PC games are buggy rush jobbies or poor console ports, however I've been happy with Bad Company 2 and the Vietnam expansion so I believe DICE will make a decent job of it.
Hopefully the gameplay is as enjoyable, if not better, than BC2 has been.
The Frostbite 2 engine sounds as though it has improved on the original FrostBite engine, for starters it has been coded from scratch to improve future DLC/Patch implementation (a DICE dev made a very informative post on the problems patching the FB engine in BC2 - hence you currently get massive patches when little content has been changed).