The Core 2 Quad Q8200 was what did it for me. I had intended to build a system to play with virtual machines, only to find after I built it up that the Q8200 didn't have VT-x - something that was NOT noted in the store display.

I put it in an Intel-branded motherboard as well, and that turned out to be one of the few motherboards I've had that failed prematurely.

Since then, the only Intels I've bought since then have been used ThinkPads.