So I was looking for a plug and play solution that achieved the following requirements:
Bluetooth
iPod
Android
and most importantly Text display. This is a huge one, having 999 tracks makes it quite a pain in the *** to find the right song. So at least knowing the title really helps with finding the right tune.

Having had 2 previous USA Spec iPod adapters for an Audi TT and Honda S2000, I have been accustomed to the ipod part being handled flawlessly and just wanted more features out of my kit. I found the grom audio USB kit with optional bluetooth and ipod integration and thought this would solve all my problems and it would be the best of both worlds.

The complete kit with harness adapter, bluetooth dongle/mic, ipod 30 pin/mini din adapter can be had for ~$218 retail, which is kind of pricey, but if you don't want to start hacking apart your interior, it's a pretty simple and comprehensive solution.

Harness:
The Grom kit comes with your choice of installation harness option: behind the headunit and trunk cd changer. I've always had a really easy time with the USA spec behind the headunit harness adapters as they typically include a plug and play oem y-adapter that interfaces between stock headunit and stock wiring harness.

Grom however, decided to reduce costs and include 3 posi taps, effectively you unplug the stock cd changer harness and plug the grom adapter in and then tap 3 wires off of the oem headunit harness with the supplied posi taps. while this added time to the initial installation, it was functional albeit a little ugly. However, the posi taps would end up loosening overtime under brutal daily driving condition (imagine what's like to ride on coilovers, solid engine mounts, solid bushings, x brace and stiffer sway bars day in and day out). This was frustrating as I would, from time to time, have to remove the headunit and screw down the posi taps.

I went to Grom's headquarters in belmont and returned the headunit harness and got a trunk cd changer harness kit which was completely plug and play. Problem solved.

Switching between sources:
This is probably the most convoluted task of the whole operation. Basically you have to cycle through the inputs with the Mode button on the stock head unit from whatever source you are on till you get to the cd changer source. If you were already on the cd changer source, you will have to cycle through it again until you come full circle to the cd changer source and wait for this FOBBY CHINESE VOICE to announce whether it is on iPod, aux or USB. Now I say fobby voice because if you are looking for an audible coherent announcement forget it. iPod = eyeeeeee Paud. AUX = eh-uh-ex but said at mach 1. The only one that almost passed for english was USB. Now once you have heard this announcement you need to use the seek forward button to switch between iPod, aux and usb. However, if you aren't fast enough, you will have to cycle through the mod button again and start the procedure all over.

Audio Quality:
USB audio and bluetooth audio sound great. Sounds as good to my ears as mp3 cds in my stock audio system.

Galaxy and android 4.2 owners note:
I use to have a galaxy s3, which doesn't support usb mass storage mode. Instead it supports media transport protocol, which effectively renders the GS3 useless in usb mode. Supposedly their is an app to put the GS3 into USB Mass Storage but I have since gotten rid of my GS3 in favor of an iPhone 5. For android 4.2 owners i have yet to see a2dp work successfully on early 4.2 releases for HTC One and Nexus 7.

iPod audio:
One thing I don't understand is why the USB part doesn't support iPod/iPhone natively. Plugging your iphone usb cable into the USB port is only good for charging. I'm guessing the reason for this is so that they can charge an astronomical price for an iPod 30 pin to mini din adapter cable but I would gladly pay for if the audio from the cable were as good as USB/bluetooth audio, which it isn't. For some odd reason, it sounds distorted in the lower frequencies. to Test this, I downloaded a podcast source on to a USB stick, also used the nexus 7 to play both the podcast in mp3 format and from a podcast app against the iPhone 5 playing the same podcast via apple's podcast app and pushing the same downloaded mp3, found on the USB stick, to the iphone via iTunes. For some reason, the audio sounds distorted and muddy in the low end frequency. I attempted to rectify the problem by making sure the iPhone did not have any equalizer enhancement on and that the audio volume wasn't at max (this didn't matter) however I have yet to find a solution or a reason, as of right now at least it isn't a caused by a bad source.

One other annoyance, the iPod source only displays iPod on the headunit as opposed to any pertinent audio text.

Bottom line:
If you only have an iPhone and only care about charging your iPhone and playing music and getting google maps voice guidance, I would skip all the eccentricities of this kit and go with the USA Spec.

If you have an Android or want to be able to make calls on your iphone or just hate cables than this kit's bluetooth functionality is definitely a solid success.

I have suggested to the manufacturer that they grab an ethnically neutral native english speaking 20 year female to redo the announcements. The fobby sample they included was almost enough of a deal breaker but I have since learn to deal with it.