downloads are as fast as the slowest link.

I've seen >100KB/s (downloading a popular file from many fast sources), but not often. If a file is only available from a modem user, or is coming from a host serving many people, you'll only get a small piece of their bandwidth. That's why it's best to download files available from many sources. 4-6KB/s is probably more typical.

If you are behind a firewall, your chances of fast reliable downloads get even slimmer.

Look at your LimeWire Help menu Tip of the Day for more info. The user guide used to have more info (I think it has been offline for updating)