I've had the iDA-X001 your looking at for 18 months and it is really good, but it does have a couple of drawbacks.
Firstly, the full speed connection is only available when you buy the additional lead, which I did. The difference in speed is so minimal it didn't really notice, however, what they don't tell you is that by using the full speed connection you actually lose the ability to view the album covers on the headunit! Showing the artwork like it does was the main reason I bought it in the first place!
Secondly, it's not as easy to navigate as it could be. When you press the centre of the jog dial to open the menus (artist, album, playlists etc) and find the one you want, you then have to press the seperate enter button. This is counter intuitive to the average ipod user as you'd expect to press the centre of the jog dial again- a mistake I still make regularly.
Lastly, I know I'm ranting, scrolling through the artists/albums can take a lifetime. You can get round this though by selecting the music you want before plugging in the ipod/phone, and it will carry on playing from where you left it.
Having said all that (nearly done) it is a great headunit and I've since put it into my e39 5 series which even with the standard speakers is a great sound (I needed it amped in the 306 to get a decent sound).
Apparently the newer versions of this unit take care of the last two issues I've had with it, and if you do go for the extra bluetooth adapter avoid the first generation of it as it had compatibility problems with more modern phones- before the 3gs was released.
Lastly, deep breath, I've got photos of it installed in the 306 in my old posts.
If you go down to the woods today...........