I think it's worthwhile, because it rewards the developers, both paid and opensource. See http://www.limewire.org/awards.shtml for examples.

I also like that the developers made the decision to make the Free *almost* as good as the pro. Crippled free programs suck.

The occasional times I've tried the Free, I don't see much difference. Sources make the biggest difference, and variations between sessions make a more noticable difference than Pro/Free

btw--since the sode is opensource, people can just build their own Pro, but that's not the point.

In other words, the real reason to go Pro is not some technical advantage IMHO