Not sure how easy or difficult this would be to implement, but...
It'd be really nifty if the client could dynamicly adjust the upload rate based on the current download rate and connection capability, so that it is always uploading as fast as possible without saturating the connection and interfering with the downstream side.
For example, my cable connection is capped at 3000d/256u kilobits/sec, if the torrent is downloading at full speed the torrent upload rate has be be less than roughly 14 kB/s (can't remember the exact number) to avoid congesting the upstream. But if the torrent slows down for whatever reason there would be more upstream available, then the client could increase the upload rate to take advantage of the added bandwidth, leaving a safety buffer to insure that if the download starts to speed back up there's enough upstream bandwidth available to allow it to do so. If the download is completed it could just uncap the upload, or switch to a user specified setting that's different than the normal download one.
It'd be really helpfull to the non-technical users if the client could automaticly discover the bandwidth limits also.
Both of those features are probably something that should be part of the core BitTorrent code though, but it'd be cool if BitTornado beat the offical one to it.