Purely for balance...
I've also had it since release and find it to be a re-hashed version of GT5, complete with the same old AI, poor sounds (for the most part) and most of the features removed so they can be brought in via updates and DLC so as the PS3 could have another GT title before the focus shifts to the next generation. In other words, it feels rushed and incomplete. And not just as far as features go; there're many flaws, some may say fundamental ones, with game physics/mechanics. Oh, and if you like shuffle racing, I'm afraid there's bad news. Same goes for those who like a challenge as well.
I'm not whining, I'm providing balance to the above praise.
I think now, what with the recent closure of GT5's online services and the only online support being with GT6 until 7 comes out, is the best time to get it. I believe it will now get the attention it so badly needs . Plus it's a slightly more complete game than it was initially (Vision GT cars are already starting to dribble in again, in relatively short succession, for example, although that's perhaps unrelated to GT5's death), with hopefully more to come (course creator, b-spec, etc).