File transfers has been a long standing problem within the jabber community and the present solution using the so called bytestreams protocol is far from perfect. A kind of improvement by using symmetric streamhosts called fast mode is being used by Psi and Coccinella, but this extension was rejected by the Jabber Council (?) for reasons unknown to me. I can guess why; it is a bit complicated to implement, especially with stream proxies.
A long term request has been for a search function in the roster. I haven't seen the need for this since my rosters are usually experimental and small, but my current work on optimizations for large rosters put the focus on a roster find function.