I've been a big fan of GURPS for years ever since I discovered G:3E back in the early 90s. These days, it is one my 3 goto systems for gaming, (the other two being Hero and Savage Worlds). One of neatest tricks for GURPS I was ever introduced to was, "Take any 3 GURPS books and you can make a game out of it." That's something you can still do with humungous library of books for the system.
One thing I have learned about GURPS, (and Hero when it comes down to it), is that it does require a bit more prep work than a dedicated system like Pathfinder or Eclipse Phase. Not much more, though. The GM just needs to define what rules are to be used such as combat, (Will it be the combat lite, detailed skirmish set or something in between? Cinematic to Realistically Deadly?), skills, (detailed skill set or Wildcard skills?) and starting points, (50 pts to 500 pts)*.
The Players need a solid character concept based on the GM's world before cracking open the books. The best characters I've seen are the ones who's player have and ultimate goal in mind. This allows character growth in-game, which makes for a more satisfying experience than having all the goodies up front (possibly a reason why I'm not big on most Supers games).
Basically, the hard part of GURPS comes from the up-front stuff before the game starts, and that even isn't that hard when you know what you have in mind.
My 50 cents
* I have played awesome 50-point GURPS games. One of the more interesting ones was playing a character in hiding in Nazi-Occupied Warsaw. It's all about prespective.
I'm wise enough to know that I don't know half as much as I think I know. Y'know?