It would be nice, for a small f2f, to be able to remember the filenames of peers that have gone offline. This would be useful so that you can still search and start downloading them even when there currently is no valid source. This is for the case where the peers are personal computers that are not always on. Obviously there would be a timeout (48h?) after which you forget this info. You would need to display it too (on Transfer and on search results).
Other thing I found out, that seems to me to be a bug :
* peer A start download of file Y from peer B
* peer B goes offline
* peer C searches for file Y and cannot find anything although it is in peer A (not full version though)