I got a brand new Mac Pro. I need it for work. Well, never mind, I'll also play on it.
My bootcamp partition, system and programs, is now on an 60GB OCZ Vertex SSD. At about 200 euros, it is certainly expensive for the storage volume, but it REALLY makes a difference. I can run five characters in Dalaran now, on mounts even, without any lag. My iMac used to choke on two characters. I really feel like disk access was the limiting factor there. I didn't test my new machine running WoW from a regular hard drive though.