The big power boxes are really nice for a set of problems. we have a couple of big ass ones for oracle servers for very large databases and they work great. They do cost big $, as somebody said in a thread long ago when your data matters you get what you pay for. IBM makes a killing on these and the 'frames because for a lot of businesses it's easier to pay some big bucks now then later when your data is fucked. It's not as hard as you think to sell these guys, plus the virtualization is top noch, and done at the hardware level (I know you get that on wintel, I'm not sure if VMWARE the most popular solution uses it. I think sun also provides hardware assist for virtualization.)
That being said, for a lot of bulk work, I prefer linux/windows. Lots of speed on the cheap, perfect for a farm of app servers.