How was the frame rate on Killzone? It didn't feel choppy?
edit: It's also good to hear about Jak. The only game I played in the series is Jak II and only until I got stuck early on (guess I was too young to figure it out) so it's a whole new series for me.
The framerate in Killzone was fricking excellent. No slowdown whatsoever during my MP match, nor my single player run through. I was incredibly impressed. The game looks and feels good. If you are a Killzone fan, then I can't see how this would disappoint in that regard.
While I felt that Shadowfall, while gorgeous, was really cool, it didn't really feel like Killzone to me when I was watching the demonstration. Mercenaries reminds me of Killzone 2. I really, really enjoyed it!
Also, I forgot to ask if the game supported bots. Sorry! Hopefully it will. Fighting against bots can be a lot of fun!