I know it's already been said, so apologies for repeating suggestions, but what drives me insane is that I can't get to my garage from Practice and Speed Test, and also that you can't then delete or manage the times set in the leaderboards / results.
It would be nice to be able to delete / group / minimise all the times from a particular car into one entry, so you can just see the best of that particular car and then have a direct comparison to other cars.
And not being able to quickly change cars when wanting to compare lap times and 0-60 etc, is just, well, typical GT5 in a way - tedious! Same as kicking you out of the the dealerships or UCD after buying a car, or wanting to quickly do an oil change, or the mess that is paint and wheels, and the mess that is your Garage, lap delta, info on what condition your engine and body rigidity are in so you can make a decision whether or not to overhaul / restore them, etc, etc, etc...
Anyway, like I said, all been said before. If half of what was said in this thread was implemented then GT5 would be a much, much better game / experience. And like the thread is titled, you would think this would be fairly easy to implement, and in my opinion time much better spent than modelling a Mini Countryman or yet another Nissan...