In a perfect universe WARHAMMER 40,000 ONLINE would be a PLANETSIDE-style tactical shooter with all of the races, weapons and equipment from the WH40K tabletop game to play and go completely insane with.
In practice, it appears they've gone for WORLD OF WARCRAFT WITH 500 FOOT TALL BATTLE MEK THINGS, which could still be fun. But intriguing glimpses of a cover system of some kind suggests there might be a more dynamic combat system at work here. Potentially interesting.