I've got a Kenwood DNX525 which is on 'VWs approved list' apparently. It's nothing special really I only use it for radio, CD, satnav and reverse parking sensor picture. Sound is ok through factory speakers. UI takes some getting used to as its not that easy. Biggest issue is it takes about 2 mins to boot up when you first turn the key.
Sat nav is ok but has very little displayed when on nav screen, I'd like distance and travel time remaining etc and currently there is no obvious way of displaying it.