Gruml allows you to view and manage your feed subscriptions of your Google Reader account in Mac OS X. The advantage of this is that you don't need a browser, you get a nice RSS symbol in your menu bar telling you how many feeds you have unread and of course, it uses a Mac OS interface. Gruml allows you to read your newsfeeds, manage them in folders, tag them and more.
All this of course takes place in sync with your Google Reader account. On the positive side, I like the way feeds are organized into folders and expanding them reveals the feeds with their logos. I also like the way I don't need to worry about Firefox crashing while I'm accessing feeds and the large window in which to read them. Given time, I'm sure I could come to rely on Gruml but it my eyes, Google Reader is already a pretty good product that's hard to improve upon. Gruml is also still in beta stage so expect some crashes and bugs while using it.
Gruml is a nice idea and if you're a die hard Mac OS X Cocoa interface fan and use Google Reader, you'll probably love it. Otherwise, you'll probably find little reason to switch.