High resolution ALAC files plays very well (tried 24/96 and 24/192) as well as 16/44.1 ALAC files.
One important thing though.. the player settings must be set at "Native iOS" to work properly, or else everything will be played as 16/44.1.
Another thing that I found out is that the mini DLNA server on the Wireless Plus does not support gapless playback. That is a shame though.. as while listening to albums that are ment to put you in a trance, you get out of it each time a new track comes along..
I have the hacked version of the Seagate disk, and have asked the developers to make support for gapless playback.. but I don't know if it ever will make the todo list.. I hope so though..