Just had a Philips CEM3000 CD player installed in my 2001 Mini One to replace the cassette deck and non working CD multichanger that I bought it with.
So far seems pretty nifty on the drive back. Connects with and charges my iPhone 4 without any issues so far and according to the Philips site, it should connect with nearly all the iPods/iPhones/iPads (although there are a couple if can't charge) depending on what firmware you have installed.
Apparently it won't work with the iPod Shuffles, which is a little odd.
Control is a little odd too. It seems that if you use the player controls, you can only play from your entire iPod playlist, but you can also set it to be controlled from the iPod so that you simply select and start your own playlists (I don't want to be fiddling with playlist selection once I'm driving anyway, so that's not a problem for me).
One thing I had to check before I bought it was whether it actually played AAC tracks from the iPod. It lists being able to play MP3 and WMA tracks, but also as "Made for iPhone" which is a bit odd as Apple wouldn't authorise something that doesn't play AAC for the Made for iPhone program. So I checked with Philips and it plays whatever your iPhone plays, the USB connection in this case just being for control and digital audio. (thumbs up to Philips customer support in Singapore who I apparently ended up connected to on their online support chat, despite googling for Philips support in the UK

).
If you're using a non iOS USB device, you're limited to just MP3 or WMA format tracks but you have folder/song search options on the panel.
Sound quality is great with the standard Mini speakers (not sure which options my Mini One had, but assuming the standard ones with the Cassette/6CD head unit?) and the radio reception is a lot better than the built in unit was.
Now I just have to unbolt the dead CD multichanger from the boot to get the space back