Why yes, yes I have used my RSS reader. I use it quite regularly. Unlike twitters stupid 140 char limit, RSS gives me enough information right in the reader to know if the article in question is worth clicking on to read more (not to mention, most sites let you read the whole article right in the RSS feed).
I've dabbled a bit with twitter, and to me at least it doesn't seem even remotely likely to displace RSS.  Now, if I could find more high quality social news sites like HackerNews, MetaFilter, etc.  THAT might supplant my RSS reader.