Nige
My PC's don't get turned off as such, they get a restart occasionally and that's it. They generally run 24/7 (Vista box got shutdown 3 weeks ago, iirc). I don't have any issues with them (now it's one XP Pro and a Vista since the XP Home laptop kinda went BANG, and the scorch mark on the circuit board is a cracker. You don't want to know what the smell was like but that was a manufacturer problem. Can happen to anyone). Even the latest Vista updates didn't crash that one, despite one of these updates causing issues. I'm a home/small business user so having the machines working is crucial to me (2 stepkids at college, etc) so I need reliability. I was ONCE hit by a virus, and those stepkids know the rules regarding opening emails/downloading. I have no issues, you only need basic precautions and decent AV/firewall software (all of which is free as we know). I actually know how safe my PC's are, mainly since I got nailed once it made me paranoid about things like that. Of course, what is needed at your work kinda dictates what you need to use, I cannot see the need to spend THAT much on something that will do what is needed by us.
Of course, as I have said before, NEVER download a driver from Windows Update. I learned that the hard way.
Again, don't get me wrong. I am open to things. I just cannot figure out why a Mac is better (will be attacking that laptop again this weekend. After all, one has to gain experience with things before you can condemn them, and I cannot recommend a Mac. That attitude may change, and if it does I will happily bake the biggest Humble Pie you have ever seen and invite you over to share it)
Dell? Don't talk to me about them. My experiences with these things were so bad I wouldn't even widdle on them