Since the demise of the free FeedDemon betas, I'd been using Sharpreader or Wildgrape NewsDesk (depending on what mood I was in) to read RSS feeds. Neither was perfect, but I'd settled on Sharpreader, despite the oh-so-slow notification pop-ups (this on a 2.5GHz machine...). But today I thought I'd give the RSS Reader Panel for Firefox (http://texturizer.net/firefox/extensions/#rssreaderpanel) another try. Guess what? It's pretty good. The Open In Contents Area option now produces a spiffy-looking display, with the option of customising the CSS used (so you can't complain even if you don't like it).
The addition of new feeds isn't as slick as it might be, but it's just as easy as creating a new bookmark ...because you just have to create a new bookmark. There doesn't seem to be an option for intermingling all of the items into a single date-sorted list, but that's not too much of a worry.