As lots of commenters said on our last post, this isn't really an ingame browser, it's more of an overlay that lets you browse while playing the game. And all it really does is save you the couple of minutes it would take to tab out and check your own browser (or just run WoW in a windowed mode, and use both at the same time).
But there are a probably a few users out there who would find it really useful. Downtime is the main issue I can think of (though lots of my downtime is filled lately with the Bejeweled addon anyway). But if you've been waiting for a solid, standalone ingame browser to come along (complete with Flash support, which makes it easy to pull up Hulu or Pandora while playing), Rogue is it.