GURPS—the Generic Universal Roleplaying System—is one of my favorite games, but this is not an installment of Favorite Games Ever. Instead, I want to look at some of the reasons I hear for why gamers avoid, dislike, even hate GURPS. I don't really agree with many of these points, but let's examine them for what they are, rather than try to dismiss them out of hand.
Too Much Math
GURPS certainly has a reputation for being numbers heavy, and it's not entirely undeserved. While at its core, you'll only need basic arithmetic to play GURPS, there are slightly more advanced permutations and optional rules that call for multiplying by percentages and rounding (almost always up) or dividing by something other than half. In a very few, very niche areas in supplements, you may need to pull out a calculator and use the square root function.
While I don't have a problem digging into a little math here and there, I can understand how it would put off a gamer who just wants to grab a character sheet and roll some dice. The important thing to remember is that there no math needed in actual play beyond simple addition and subtraction of modifiers. What tougher calculations there are lay in prep between games, and almost all of it is on the GM's shoulders.
Too Many Rules
Steve Jackson games has produced a tremendous amount of material for GURPS during the game's 31 year publication history. And a lot of that material has been rules to emulate some genre, activity, or real-world process in the game. So, yes, it can be daunting to take it all in.
More worrying, of course, is the number of rules present in the core rules, the Basic Set. Everything from realistic treatments of gravity and radiation to systems for fantasy magic and psionic powers, from primitive spears to automatic weapons, are presented with equal emphasis. How can you possibly run a game and remember all of this?
The key here, of course, is to understand the game you're trying to run. You cannot and should not use every rule presented even in the Basic Set. Part of the GM's job when setting up a campaign is deciding which optional systems they're going to use. That, however, leads us to the third and final complaint.
Too Much Work
I'm not going to lie. I can spend a couple hours lovingly crafting a GURPS character. I pour over the rulebooks, thinking about which options to toggle on or off to give my (hypothetical) campaign just the right feel. This is a pretty stark contrast to a lot of modern games that value getting into play as quickly and effortlessly as possible.
I really don't have an answer to this one. At its heart, GURPS is a game for people who like to tinker. A lot of the optional rules I talked about before exist to facilitate this style of play. (GURPS is the game that taught me that campaign planning—i.e., game design—is play in itself.) And yes, this style isn't for everyone. But I like it. Maybe someday I'll tell you more about why I do.