The only downsidethat u get is that you lose the display. Also as with most aftermarket radios u lose the steering wheel controls, but u can buy an interface for that. You also need an interface if u want to keep your onstar. Remote start works fine as do all the other features. If you get the right harness you can hook up your factory stereo at any time to change settings. You can buy the kit anywhere it's the metra 99-3303. Hope this was helpful.
I actually bought the kenwood double din, it looks great but it will not fit in the opening, you need to have a custom mounting kit made, they were charging me $450 to do this so i ended up selling the unit. Also there is a kit out there to get the information center that just came out about a week ago and i just bought it on ebay. ( model - metra 99_3303) It is pricy but its worht the money to have your info center, a;so if u buy a double din unit it will be impossible to install this jit. hope this was uselful, ask if you need to know anything else. Oh by the way my pioneer Avic-n2 is great, gotta love the navi