This is the only controller I have found that allows you to find a playlist, artist, album or song through it (via drop down menu) and not bringing iTunes to the front. Lots of possible configurations and hotkey assignments possible. Tech support for minor problems has been excellent. Highly recommend.

I have kept up with Bookends updates for a number of years now. It gets better and better, with lots of customization now that can adapt to the needs of academic researchers. Excellent use of incorporating PDF documents linked to references. A long list of academic/medical servers for downloading references, or you can easily create your own and use the embedded Search for online work. I use Nisus Writer Pro with Bookends and they work very well. Also, Scrivener is a good addition to this workflow. I've found the developer of Bookends to be very responsive and the forums are very active. I have a large database, sub-divided with smart and manual folders and have no problem with speed of input or output.
At this price point and with these features, Bookends is well worth a long look if you need citation and reference help.