I would like the addition of host filters. Specifically country filters.
Most hosts I get are in the US. Often, I am looking for things found only in Europe. When I am connected to European host servers, I get good search results much faster(for those things that are mostly based in Europe).
Currently the only way of filtering host countries is to disconnect from US servers in a mad frenzy even as I am connecting to new US servers. I am sure this rapid connect/disconnect, sometimes hundreds of times in a row, lags down parts of the gnutella network.
There may also be other things that would be good to add for host filtering. I think this could improve the performance of the gnutella network as a whole if implemented correctly.