I have resellers for a software project I migrated to SheevaPlug about a year ago who have severe problems to fulfill their customer orders because SheevaPlug production is quite unstable/unpredictable. That is extremely annoying and makes the product very problematic from my point of view apart from hobby interests.
I am just in the process of migrating the application to the GuruPlug which again starts as a nightmare (endless waiting, incomplete delivery, zero documentation, you have to google around to find some bits). Documentation and availability, is clearly sub-par from whatever I have experienced so far. I was working with products from Thailand, Switzerland and Israel before and never had this kind of uncertainty. So be warned, your pretty much on your own and delivery of products is going as they like. Engineering is also not very convincing, my customers encountered some power supply failures after a couple of months, you can read lots of this here in the forum as well.
Beside the "plug" hype the product has severe problems (from my point of view) and yes it is quite capable when finally running. Welcome to "adventure land" :-)