I've been using PlugPlayer for a whole day now (!) and really have to complement you on a great app - well worth the price on both the iPlatforms.
A suggestion: the compact UI on the iPod is great, with excellent screen realestate usage.
On the ipad tho, I'm finding the whole "toggle between album and playlist" thing a little frustrating, esp. as i don't use Album Art (yes, I know I'm probably one of a small handful!<grin> )
I'd love to have an alternative view on the iPad whereby (say) the Album List (/Artists/etc) is shown on the left of the screen, whle the RHS shows the current playlist (ideally, playlists, tabbed) -similar to the basic Album/Playlist layout in Foobar2000.
Many thanks for your consideration in any case