GT5 looks like a rather large let down from what I have seen thus far. To the point where I'm probably not going to buy it.
The biggest thing is how gimped the standards actually are. No custom wheels, they don't look nearly as good as they could/should, limited to no actual damage. The standards are there just to say "this game has 1000 cars!" I'm surprised you can even perform performance upgrades on them; but, you probably can't... hell you probably can't even drive them.
Also, it seems as if the game in general has taken a step backward. No brakes for example. What were they honestly thinking when they decided to cut racing brakes? Brakes are one of the most important upgrades of any performance car build; and you've been able to do it since GT1.
The paint scheme also looks stupid. Why couldn't we just get a grid of colors to choose from, like every other game? We actually have to earn a car with that color in order to paint other cars that color, and then, from the looks of it, you can only use that paint "item" once.
And on to premium cars. We barely get any new cars. Some Ferrari's that have been around for awhile, some aging Lamborghinis (what about all the NEW ones), a Suzuki Cappuccino? Then they have the audacity to remake a few standard cars in premium trim; but still leave the standard cars in! Come on. Since GT5 began development, there has been some huge cars out there. The Cadillac CTS-V, the new Dodge Charger, the Shelby GT500, Lotus Exige. All of these important cars are missing.