I've had the adapter for about 6 months now, and I love it. Here are my pros and cons:
Pros:
Adequate cable length and strength - well made
Seamless integration
Sound is unbelievable - better than XM
Can scroll through all of the menus/playlists
Shows artist/song/album
Control iPod/iPhone from Z-2
Cons:
Cable is not retractable - you need to find a way to store it, or it is always exposed
No video capability, even with bypass
Scrolling through menus is tedious and slow; no way to search
Does not show album art
Does not charge iPhones or iTouches - will ask to go to Airplane mode to cut down on electrical noise, though I've never heard any
The adapter plug is big and bulky and will require you take some cases off
Overall, I think it is worth the money. I would buy another one if this one ever crapped out on me. I attribute the slowness of the menus to the Z-2, itself. If you need to find a song THAT quick, unplug the iPod, search it, then plug it back in. Another added benefit is that it will play sound from any app you're in on the iPhone/iTouch. So if you like NFSU or Heavy Machinery and wondered what it would sound like over a kick-ass system, plug it in.