It basically means they'll get it once every 15 minutes, and even if hundreds of people subscribe to the feed it won't put any more load on this server.
All of the other feeds (direct to forums and threads) are still handled directly to this server, but as the majority of people subscribe to the global RSS feed I don't think those will be a problem at all.
I've changed the main RSS feed to be served via FeedBurner:
http://feeds.feedburner.com/LondonFGSS
It basically means they'll get it once every 15 minutes, and even if hundreds of people subscribe to the feed it won't put any more load on this server.
All of the other feeds (direct to forums and threads) are still handled directly to this server, but as the majority of people subscribe to the global RSS feed I don't think those will be a problem at all.