I've been playing the ever loving hell out of the demo on steam (you can download it now if you preordered). Just the first 1.5 maps of the first campaign is incredible. It's awesome how many times you can play it and still come away with a completely different experience each time.
As far as the witch:
She can be avoided. Don't shine your light on her, run past her, or shoot near her or you'll wake her up and she'll shred who ever is nearest to her. The hardest part is when she's right in the middle of a place you have to go through :-/ Damn witch.
The tank is definitely the toughest, especially on the hardest setting. He has something to the tune of 10,000 HPs.
As far as which version to get:
PC, no question, and here's why
1) People are already starting to dissect the Director, and you're seeing zombies pop up in counter strike maps now. In other words, the director does most of the work just by virtue of its nature. Imagine when people start making maps for this (and they're already starting to).
de_dust1 in L4D PC http://www.youtube.com/watch?v=_SlXeiRH8VI
360 guys will get the original 20 maps, this game is going to have so many player made maps it'll be disgusting. Especially since most of the content legwork will be done for you (via the director).
2) Server settings, something that you can't do on consoles. It'll make for a lot of different ways to the play the game besides vanilla L4D, and again people are already messing with cvars in the demo.
http://www.youtube.com/watch?v=RcJ9EeD3EJ8
Anyway, no comparison, especially for a game like this that will probably end up the most heavily modded and added to of all the source engine games.
And again I stress, Tanks and F right off >:(
3rd Party Wall of Shame
http://www.nintendoworldreport.com/forums/index.php?topic=30478.msg581036#msg581036
