Surface is pretty straightforward and doesn't really have that much of a 'mystery puzzle' element (except for where the creatures come from of course), but so far I'm OK with that.
At this point, Invasion seems like a slow-moving smalltown version of Invasion of the Body Snatchers, and Threshhold seems like a silly military-action-show version of Invasion of the Body Snatchers. I'm actually finding myself liking Surface the best of these three "alien mystery" series (and no, not just because of all the bikinis!)
The monster CGI in Surface is OK for television, but maybe if the show catches on there will be some more extensive FX scenes.