I'm new to the GURPS world - been playing D&D D20 for a few years, but when I decided I wanted to try GMing a game I wanted to try out a different system because I always felt the D&D rules were too unrealistic, especially when it comes to combat.
I'm planning a sci-fi campaign, and looked over a large number of game systems to see which I'd want to use... and considered D20 Future, deciding that it looked it it would likely fall under the same limitations as D&D, just with different images pasted on the game system.
GURPS, I will admit, has an absolute crapload of rules, *especially* when it comes to combat (we're talking 55 pages of rules, not even including the damage effects section - in comparison D&D has about 30 - more like 15 if you consider how much of that is taken up by graphics), which, if I'm sure I included/allowed all of them, would cause a 1-second combat round to take like 20 minutes to play realtime.
As a result I'm planning on using a basic set of combat rules, with the possibility of allowing players to use the more advanced rules only in special situations where the situation really calls for it.
I've already warned the people I'm planning to play with not to get overwhelmed by the books - because they try to cover *everything* in one book, there are a tons of rules & options - but over half of which probably won't apply to your individual campaign, so they can be ignored (for example there are if I remember right something like 60+ pages of advantages (aka feats) and disadvantages - but as I'm planning a semi-realistic sci-fi campaign, I can just tell the players to "ignore anything marked with an alien or a lightning bolt." Which is probably half of them if not more).