When I first moved in, the bathtub didn't drain well. I tried to plunge it, and a ton of paint chips and crud came up (from repainting the apartment I suppose, not sure how it ended up down the bathtub...) I talked to the maintenance and they had it fixed the next day. About a year after I moved in, two people showed up at my apartment randomly to replace my door. I received no notice so I was skeptical. Called the management office and they said they were replacing all the doors, I just wish they'd have let me know ahead of time. Other than those 2 occasions, I haven't had any maintenance issues with my apartment.
Noise isn't bad at all where my apartment is (along Jeffrey.) You hear the occasional police/ambulance/fire engine, but for the most part you don't hear much of the traffic. I don't have to be at work 'till between 9 and 10, so I sleep in till after 8 during the week and have only been woken up by noise once or twice in 2 years.
I noticed several of the other reviews mentioned roaches, but I haven't seen a single one. From time to time I'll have a tiny black spider or silverfish walking on the wall, but never ants or roaches.
Parking is great. You get a reserved covered spot, and there are just as many open parking spots are there are reserved ones. If you've looked around at Irvine apartments, most have very little open parking for guests.