I agree with you man, not having the option to change your brakes is shitty. I can name a few cars with extremely spongy brakes the vette zo6, Buggatti, Saleen S7.
The game is great, but to be honest I am a bit let down. For as long as they took to produce this game it has some flaws. Like they screwed up the specs on some cars, ie the z06 is supposed to have 505 hp and the torque is supposed to be a little higher. This is perhaps maybe they already put the car in the game before the updated SAE ratings came into effect. Also the course editor is kind of lame. The snow tracks are pretty unrealistic...I put snow tires on my Dodge Viper and was able to drive around...lol let me tell you something, I have a 96 Trans Am RWD pushing around 350hp, when it snows more than an inch that car is not moving lol..let alone a 600hp beast!. They are missing several great cars, like the Bugatti SS, the SSC ultimate Aero...And the Saleen S7 Twin Turbo !

You cant adjust individual gears in the supposed "fully customizable" transmission, just only the final drive.
Once you install the titanium muffler the cars all pretty much sound the same.
The bots seem like they drive on a predestined line, I can deal with the pit maneuvers, in fact I think it adds to the game..But there is no orginiality/individuality between the cpu cars..In real life drivers have different styles and take different lines on courses
The cost of mods: They should have some variation!
The type of mods!
Some are blatantly stupid!..They let you put a "sports" suspension with adjustable height on cars like the ZR1 and MClaren F1 that obviously come with adjustable dampers n such.
The damage engine is comical, I mean the scratches look pretty cool..But next time hit something with the nose of your car, it looks like the facade just gets stretched, the grille nor headlights crack lol.
No mechanical damage during races.
And lastly no engine ECU custom Tune jobs
All of that said though, I think they did some really really really cool stuff.
Like the windshield wipers with rain and dirt and all...Also the snow, I know I said it was comical how they made the traction, but the realism that it brings when snowing is pretty cool..Next time your on a snow track just stop your car, you will see the snow accumulate on your rear window!
The tire smoke is uber real...It feels like your Tom Cruise in Days of Thunder when cars spin out and crash! all the smoke created.
The fact you can adjust your front and rear spoilers.
The detail inside of the cars, WOW!
All of that said, again GT5 is a GREAT game...Game of the year perhaps, I would recommend it to anyone and I have no regrets buying it BUT for the moronically long wait they put us through it could have been better!
Oh and they didnt include launch control for the cars that come with it in real life