Thanks for your kind comments and suggestions guys, its great to see this kind of support.

File caching and streaming are interesting issues, at this stage most Ultrapeers would be unable to sustain that amount of traffic, but it's definitely something to look into in the future.

Regarding freezing on startup, I think the time is proportional to the size of the library.. I'm actually checking that out now to see if improvements could be made. The library scales well to a couple of gigs on a local drive, but above that there is a noticable delay if it has to scan on disk (searching is still very quick though).