As TorrentFreak explains, UDP trackers are much less resource intensive than HTTP trackers, and most torrent sites out there already support it. Essentially what this means is that torrent trackers will be able to support many more users with their current hardware and not crash under the load, while on the other hand users would avoid browsing slowdowns since UDP trackers do not interfere with HTTP traffic.
Vuze, BitComet, Deluge, KTorrent and several others have already implemented this feature but uTorrent’s popularity should further boost widespread adoption of the protocol.
There are a few other changes in version 2.0, including a transfer cap feature which will help users with cap-limited bandwidth avoid overage charges or having their service cut off. You can track your usage in megabytes, with a handy graph to visualize it, and even configure uTorrent to shut down once the predefined limits have been hit.
Last but not least, uTorrent enjoys several improvements to its uTP support, which allows the client to automatically regulate its bandwidth usage to avoid adversely impacting your internet connection and other locally-running programs. The full list of changes can be read at the uTorrent forums.