Going from movable frames between browse pane and playlist to static frames is going backwards. I found that being able to vertically size the playlist to see more was very useful especially on netbooks or widescreens. Not really understanding why this ability had to be removed in this new version.
Also I use HD 720 theme with my HDTV and now the window or frame elevator controls are now white where they sorta matched the blue color in 3.6
Otherwise subsonic is great!