Hmmm....the X-Men cover is intriguing, and Hawkeye actually looks pretty badass there. The Spidey cover...something is just odd about it, but I can't figure it out. Not a bad design, though. Kinda like the colors.
Also after reading ultimate thor my recommended reading list would be:
Ultimates->Ultimate 2->Ultimate Thor.
Ultimate Thor even fixes any errors Loeb has made with Ultimate Thor when he took over a few titles. These are very short too so it won't be too hard to digest.