I guess I’ve been a longtime Newsblur user at this point. The service is really solid and it is a great reliable replacement for Google Reader. I’ve had people recommend a couple of different services but the pace at which @samuelclay has been implementing new features and performance improvements makes me incredibly indifferent to even trying anything else.
If you use Tumblr for more than reblogging posts, you should absolutely check out using RSS to keep up with the news. There is an entire internet out there that isn’t run on the Tumblr backend and I think you’ll find that having all that news delivered directly to you as it happens can be a fantastic productivity boost. There is an added benefit of providing you with a greater sense of situational awareness that is an obvious boon for any internet sniper.
They just added a great new feature that automatically tags articles as they show up detailed here and it provides a custom feed of the stuff that’s been tagged (either by you or the system) which means you can change contexts for your news reading incredibly quickly (with just about any RSS reader.)
Also of note, their company blog is a Tumblr. :)