I apologise if this subject has been discussed to death in the past: I've only been on the list for a couple of months.
IMO, the only reason to have a mobile skin (with limited features) is contacts and may be calendaring integration. The preferable way to serve mobile devices is to use CalDAV/CardDAV. Almost all mobile devices have fully integrated clients for IMAP/CalDAV/CardDAV. So, is it really necessary to have a (feature limited) web interface? Just me 5 cents.