A few days ago, while catching up with the Youtube channel of the Gentleman Gamer, I came across this video, where the gentleman in question reviews the Basic Set of GURPS 4th ed. This is quite a lengthly review, clocking around the 25 minutes mark, but I believe this is a thorough and honest review.
What I especially appreciate is that given the generic and universal nature of GURPS, he set out to actually try the game across a variety of settings and base his review on this experience, rather than on a single reading of the two core books.
A quote from the review captures what is to me the essence of GURPS:
This game has been play-tested, you can tell.
Note that I don’t think the gentleman in question kept using GURPS after reviewing it, but this is to me the most invaluable quality a game system can present.
If you’re not familiar with the Gentleman Gamer, I really invite you to browse the contents of his Youtube channel: he has done loads and loads of reviews, many live sessions and even managed to interview a few well known RPG authors, like Mark Rein Hagen and Ed Greenwood.