Well, I enjoyed X, but not everyone did.
It's a very challenging game for one. You will
get frustrated. If that's not your thing, they you probably should wait for the price to go down a bit more.
However, if you like the characters and want to see another story about them, then by all means, get this game. It makes up for all of the out of character strange-ness from 3. It may be racing, but it's still a Jak game.
I hope that helps a bit