It would be great to have feeds for everything in Brainstorm; Comments, newly submitted ideas, most popular ideas, and anything else that I haven't thought of yet. As it is today it's quite hard to follow a discussion here. And good discussions about the ideas are half the point if this site, right?
RSS feeds are available for every idea lists, but not for comments yet.
Check the RSS icon in the right of the Firefox toolbar.
Another thing is, When being subscribed to this feed I get updates as soon as someone votes on something, and I see the same thing multiple times throughout the day. It should only update once per day, and the feed for "most popular this week" should only update once per week and so on.