Thought I'd finally chime in now that I've got posting permissions.
I went with the 7200NEX and the idatalink.
Overall I really like the stereo but I don't believe the idatalink is worth the extra expense.
idatalink does give you a range of gauges, but it won't display everything that I'd imagine an ultragauge will or any other app that a phone and OBD connector would display. I actually don't even have oil pressure as an option. The novelty of having those gauges wore off within the first week too. It will also display exact tire pressures which is kind of nice, but again a luxury I never really missed. It will also display the outside temp but its buried deep in all the submenus that I almost never look at.
I'm also unsure if the idatalink is necessary to be able to change all the chime and dome light settings. The reason I think this is that I have two options in a settings menu and its split up into "vehicle settings" and "maestro settings". All of the chime stuff is under the vehicle settings. But both the stereo and idatalink were installed at the same time so I can't verify I'd have one without the other.
To pile on, the only thing the idatalink does other than give you the gauge info is retain the steering wheel controls which can easily be done with other cheaper adapters. The annoying thing is that holding down the volume down button, or just quickly pressing it multiple times mutes the radio. I haven't had it long enough or cared to look into if there is a way it can be reprogrammed.
I couldn't find a way to purchase the idatalink equipment through any other provider than my local stereo shop, which also meant that they insisted they install it. The shop also claimed that only an authorized idatalink dealer can perform the initial setup. I have the generic microphone instead of being able to use the factory one, it does not retain the factory XM (which idatalink claims it does) so I still had to purchase an additional satillite tuner and it wouldn't work with the car's existing antenna either. You also still end up with a generic speaker for all the chime sounds that gets glued somewhere behind the dash.
I got a hell of a deal on a refurbished stereo, so that saved up enough in the budget that I didn't care paying a shop the extra 100$ or so to do all the install. Plus I was too busy lately to tackle an install like that on my own anyways. But if I were to do it again, I would just go with the stereo and the metra dash kit that includes the steering wheel control adapter first because you can always decide to upgrade with the idatalink later. I could actually send you my metra stuff since I ended up using a different dash bezel anyway.
The idatalink is definitely required for cars where climate control and stuff like that is controlled through the stereo screen. But I'm not convinced it does enough for the sonic to really justify the expense.
I am happy with the stereo and it went a long way to make the sonic feel a little more fun since I had one of the regular non-touch screen stereos to begin with though.
Keep us posted what you decide.
