It's really nice because it's extremely simple and complex... I have never heard anyone really complain about it in any real sense (like people do about D&D and such) , it's just not super popular. It's a skill based game where there are 4 attributes Strength, Dexterity, Wisdom and Health. And there are 4 secondary attributes that key off of those (like HP , Will, Perception and Fatigue). Everything is built using Advantages, Disadvantages, and most importantly skills.
The cool thing is it's a roll under 3d6 system. So basically you pick a skill and to succeed you roll under the number (so the higher number is better), similar to D&D if something is easy you get a bonus to the target number you need to succeed ( thus making it easier to achieve), if something is more difficult for your character you get negatives to the target number (making it harder to achieve). So now you basically know everything about the game, the rest is in the details.
Things can be as advanced or simple as you want, they present the game as a toolbox more than anything. In D&D there are a bunch of subsystems (like magic and such) but in gurps EVERYTHING is handled by the 3d6 roll under system. So spells are skills just as fighting with melee weapons are. If you DO decide to look into it, you may get over whelmed , but you just have to remember everything is an option and not required. They even give you a simple combat system , and the ability to run very complicated precise battles.
Also everything can be run using the system, it doesn't really give any particular "feel" like D&D does with it's high fantasy. It really is a generic system, which some may hate , but I have a million different ideas running through my head at any given moment so I really like the flexibility it gives . I can run a high fantasy game or a modern game, or a space opera using the same core rules.
Some other notes , classes and races are handed by just applying a template of skills so it's a lot like... the elder scrolls with stuff like that... i guess it's the easiest way of explaining. Also the (MANY) source books are very well researched and provide some fantastic information for just about any game system honestly. I just received my "low tech" sourcebook which gives excruciating details about life from prehistoric ages to the age of sail (around ... the renaissance or so).
I highly recommend giving it a look if you are interested in it.
