This is exactly what we are doing at http://www.feedsapi.com , we don't use a graphical UI for the logic but keywords and RegEx to create filters... Many folks are already building their own techmeme with our API, it's however not a free service. I'm not sure if this fully fits your requirements but you should take a look.
Checkout https://github.com/olviko/RssPercolator
Pipes would often get blocked by 3rd party data providers, which motivated me to roll my own library.
No graphical interface. Personally, I found Y! Pipes UI hard to work with when I needed to build large pipelines.
For what it's worth, that is exactly one of the things I am building. Glad to read I am not the only one needing it.
Founder of Enginuity Analytics here. You can ingest RSS and Tweets into our platform where we apply machine learning to provide social data, sentiment analysis, rankings, filters and demographic analysis of all the content for 27 languages. And easily export the data to Excel and more. http://theenginuity.com
One of our open source projects[1], lets you consume RSS, Email, and Tweets, with more "stuff" coming, and apply filters and set triggers, etc. It's still pretty raw, and we don't have the really awesome visual interface for laying things out, but that sort of thing is something we hope to get to eventually. One other neat thing we do is pipe content through Apache Stanbol to do semantic entity extraction, and build up a knowledgebase as content is consumed.
Maybe im dreaming about a free version of Percolate, which I have heard is really cool.