Ars Technica has a nice writeup of Microsoft's Volume Activation program for Vista complete with comments from readers. One reader notes: "I fail to see the advantages to any company of moving to a volume activation system vs. the current system." The answer is easy, unless you do, Vista will not deploy (or stay working) in your environment.
XP's activation was/is a pain - I've had classes where the activation becomes de-activated and have had to rebuild a machine. I can only see pain in the corporate sector - and an increase in support calls.
At the risk of upsetting Redmond product teams further, this is another reason for me to stay away from Vista for the forseeable future. XP SP2 is pretty darned good - I've not had a virus or any spyware for years, and VLK non-activation works well. For me XP SP2 is very much fit for purpose!