I have an Alpine IVA-D900 (DVD 7" screen) which the KCA-420i is listed as a supported HU, and which my dealer installed. But he would not install the 420 on a Alpine DVA-7996 (DVD/MP3 1-DIN no screen) on my other car. So I went out and bought one myself from The GoodGuys so I could return it if it didn't work. Well, it works fine. Display gives info as "Song/Artist/Album", the same as an MP3.

Pressing the Title button gives:
[Tag]:Song/Artist/Album
[Folder]:-- (dashes)
[File]: "ipod" (nothing else)
[Time]: Folder/Song/Time - but Folder is used for song number
[Frame]: "NOT SUPPORTED"
Searching is accessed by "Folder Search" (Function-3).

The typical function with an MP3 is:
[Tag]: Song/Artist/Album
[Folder]: Sub-directory name
[File]: actual MP3 file name (not the tag)
[Time]: Folder/Song/Time - Song is actual song #
[Frame]: Sampling freq and sampling rate ("44.1k 192k")

Still, I can control it and do FF/RW and see the name on the display. That's all that matters to me.