The reason I did not add the buttons to the main window is because I thought it would be redundant and add complexity to it.
There is already 3 other ways to add files to the playlist
1) Enable: Options>Integration>Context menu>Add to XMPlay-list
2) Drag and drop files into the playlist
3) In the Extended Playlist view there is an Add button with a green plus icon.
Dont forget you can do this with whole folders, individual files, and .pls (playlist) files.
*I thought about rounding the corners in minimode, but then its less natural when you dock it to the corners of the window.
*I havent seen this playlist bug, is the equalizer panel completely lowered when this happens?
*I dont think there is a way to change the highlight for current selection and the found files if I understand correctly.
* Playlist Total Time / Count is in the main panel right next to the equalizer grip thing in the bottom right of the playlist.
Of course the source is up on the support site if you want to change anything to fit your preference.
Hope that helps!