I notice that there aren't too many users of this app at the moment but that doesn't worry me - It does what I need and, after a couple of minor tweaks, it'll be great for my customers too!
* Fixed lend period - don't leave it up to requester.
* Automated email to lender requester when lend is approved
* Extra fields for custom use (we /lend/ books off people to add to our library - I'd like to keep track.
I had a couple a small teething problems and found the support via their forums/team excellent.