Just being in a some of the feed search engines will not help you out that much on Google or Yahoo!, but there are directories that will be crawled and they will count just like regular links, plus they should be themed if you submitted your site to the proper category.
One important thing to remember is that people are using these Feed search engines to find new content that they WANT to read. People do use these engines, and it would mean just getting more traffic to your site. Also people tend to subcribe/add feeds to their reader, which means you may have a reader for the next few weeks or months.
RSS engines can definitely bring you new visitors. The main thing I see when traffic comes in from an RSS engine is that they seem to turn into "readers" instead of simply "visitors". There are a ton of rss directories online.
In addition, by being in a directory, I've been picked up by sites who use the directories as references (found on a search they did for whatever term) to create their own bookmarks of sites who then come and hand grab my feed for their own site.
If you have an RSS feed, IMHO, submitting to RSS directories should be the first step you take after getting the feed up and running.