That brings up something important - GURPS uses hexes instead of squares, but miniatures can play the same role in the system (that is, plenty or not at all). You do need to worry about facing and so forth, just as much as in a d20 game.
It is a pretty deadly game, compared to higher level d20 stuff.
Character creation is by definition pretty wide open, so the GM needs to alert players as to what the game will involve and what things will or won't be used. A lot of supplements have templates for starting characters that show you what a bare-bones character in a given role will look like.
You should check out sjgames.com, you can still get the Lite versions of the 3rd & 4th edition rules for free. They switched to the new edition in 2004, cleaning up some of the complexities in the older system, but 80% of the sourcebooks are for 3rd edition.
Another thing to mention is that their historical and genre sourcebooks are the best in the business, good even for d20 and other systems. Some of them have even been required reading for college courses! There are books on just about every interesting historical period (India is the conspicuous exception), and every major style of play (maybe a bit thin on post-apocalyptic). As for licenses, if you like Discworld, Hellboy, David Brin's Uplift Universe, and Conan, they all have GURPS versions; as do games like Blue Planet, Conspiracy X, Mage the Ascension, Vampire the Masquerade, Werewolf the Apocalypse, In Nomine, & Deadlands.