Well I'm a little more excited now. I'm loving the look of the Lurker.
The Spitter looks... different, but I guess those sacks are one way of being able to distinguish them from the other aliens, good in a video game. It's not awesome but it is somewhat interesting.
True they are at a disavantage when it comes to stealth but judging by the name they are a sort of "sniper" class, perhaps this compensates?