The HD versions use Serious Engine 3, the originals use Serious Engine 1 which is 7 or 8 years old. It's got nothing to do with the resolution. A few things were removed, at least from the First Encounter (such as directional gravity) because of the time needed to rewrite AI. Look on Youtube for some trailers.
If it's finished in 2010 there's a risk it won't actually ship until 2011 unless finished means finished and tested ... or ofcourse if ubisoft makes it, it won't be tested at all and just shipped .... or worse - if focus home interactive (french) handles distribution it won't even show up in stores or etailors! Let's hope it won't be that bad. SS is a great game for relaxing
I've bought every SS game out there so far. SS HD is awesome! Its alot more than just a graphics upgrade. Honestly SS 2 was kind of a dissappointment to me. Hopefully croteam doesnt fumble the ball like they did on SS 2..