I am currently building an RSS aggregator, too. Mine is little more complex, though - I wanna be able to rate items as interesting or boring and use some kind of filter (currently, a simple Bayesian classifier, I intend to replace or at least enhance with something more sophisticated over the holidays) to weed out news that I am not interested in.
The biggest problem is that web design is not my strong suite (to put it mildly), so the thing looks pretty ugly. Classification does not work very well, yet, but I am not sure if this is because the classifier sucks in general or if my training set is too small at the moment (I've only been using the thing for a couple of days now).
Anyway, it is quite interesting to see another approach to the problem.