In short - yes.
Long version: I've played GT since the original for PS1 and loved all the previous games. I'm not a fanboy of any brand though, I played Forza 2 and 3 (both released within the same timespan as GT5 development....) and really enjoyed those too. Forza 3 is the obvious comparison to GT5.
First off GT5 just feels so incomplete, which is so unacceptable after such a long development. The standard cars just dilute the package - would have been better off without them and it pisses me off you're forced to use them in some races. Did they even test things out? There's such a huge inbalance in reward and challenge between different races and events. I spend 13 seconds in a nascar event doing a corner and I get $20,000. I spend 7 minutes going around the Nurburghring I get $3000. Really?? No thought went into the progression system, because of it GT5 fails in the game aspect.
Simulation wise I'm quite happy. The cars handle great, it feels right, the weather and time of day changes are good (though F1 2010 kicks the crap out of GT5 with it's weather).
Lack of complete G25/G27 support is laughable considering how many of us use it. Ya I only have to push triangle at the start of the race to enable clutch, but how hard is putting a "choose your wheel" option. Come on.
One of the biggest excitements for me was the Top Gear Test Track. Oh wait - lets make it near impossible in a frustrating as hell challenge that's not fun in the least to unlock it. Real smart. Why not make it beat Tom Cruise's time in the Kia or soemthing like that at least?
Overall there's much I like but it just frustrates me so much sometimes, it's incomplete, wasn't tested properly, it's obvious they screwed around with cool features until finally decided to release it and just threw it quickly together. I would rather have waited until March for something more complete.
Oh and the biggest disappointment of all is easily the damage, lackthereof that is. It takes so much away from the game without it. There's little consequence to punting other cars, flying off a corner etc. I won't ever touch online because of this - in Forza 2/3 if you want real racers you just put damage on full and the kiddies will slam in a wall, blow their engine, cry and leave. Here they can punt you off all they want with little consequence.
The sound just doesn't seem right to me either. Esp the VW GTI - in Forza it sounded JUST like a real one, in GT5 it sounds like every other car of the same size /class.
Cars themselves I don't think are that much better than Forza 3 either. VW GTI Mk V again - if you look at the headlight on a real one there's a little VW logo on the front of the headlight bulb itself - in Forza 3 that's modelled in 3D! GT5 I can't even see if it's there.
Oh and the AI is as drone like as ever. Gotta love when an AI attaches itself to your bumper and doesn't let off until you're either both stuck against some wall or they've spun you off the course. Forza 3 AI has awareness of you and other cars and comes across as far more convincing. When you do repeat events the AI is so robotic you can predict what they do in every turn every single time.
Soundtrack is the usual terrible stuff we've had since GT3 on. First thing I do is turn all music off (except cheesy menu music which is just GT charm lol). It's amazing how the crap song they use in the intro video just kills any excitement in it lol. Don't really care though, normally shut music off in racing sims/games, the engines are what I want to hear.
The pluses: lots of good tracks esp the real world ones, and it's fun driving around the classics again too, the special events can be fun and add variety to the game, premium cars are pretty good.
I'll keep playing it, I do enjoy it for the most part, but I really hope PD does some major upgrades to bring it up to par. Right now it seems GT fans in general will enjoy it but anyone new to the genre probably won't be too impressed.