Google now has a blogs search service, and I assume Yahoo must be doing something like this, so they both end up reading my feeds. I have both RSS and Atom, and Google seems to prefer the Atom.
There are also lots of blog directories and search engines, which will like to read one or the other. So if you have a feed, you're getting links out there, and you can get your site listed in other places. That's got to be good. And if your information makes sense as a feed (if you're providing updates on a regular basis, and people will want to stay informed) then you might be able to get some subscribers, who will keep being reminded of what's on your site.
I think news aggregator services are still mainly used by people 'in the know', so a lot of them are bloggers. That might be good, if you publish something interesting enough to get them blogging about you.
RSS feeds for regularly updated content are a good thing. It definitely increased visibility in Google (that is you see that Google has indexed a lot of feeds that has appeared on aggregrators). Not sure about Yahoo though.
[edited by: engine at 6:48 pm (utc) on Nov. 16, 2005] [edit reason] No self promo. TOS [/edit]