I have had the best luck with Dell and Sony. I prefer Dell because they tend to have more options that I am looking for in a high end machine. The Sony's I've had were very reliable. Both seem to have better quality screens that the othr brands I've had.
I'm using a Toshiba now, and I have no complaints about it that aren't Vista related (and I'm sure when my shiny new 1730 gets here it will have those very same issues).
Acer - meh, was very slow compared to another machine with similar specs, sold it within a week of purchase
Gateway - been many many years since I've used a new one, only ones I have are old and have problems for good reasons
HP - only worked on other peoples, and they were just spyware/virus issues so no real problems from my perspective
Compaq - Only bought one from 10 years ago and it still works fine to this day, neighbor uses it as her only computer (380mhz, 192mb ram, 6.4 gb HD)
IBM - been using them for years at work, not had good luck with them, seem to have a lot of odd issues, can't really tell if it's the hardware, drivers or all of the stuff our IT dept loads them up with.
Hypersonic - only Clevo I've ever owned and I never liked it. Of course the P4 was part of the problem but as much money as I spent, you'd think it would be faster than a Sony Vaio that cost half as much. Trying to get upgrade parts was a pain (would have to upgrade the mainboard) and I finally gave up and sold it.