I've had my eye on that thing for some time. Not that I'm going to be the first to bite (or ever), but it does sound pretty fascinating. Now all we need is for someone to go ahead and make a good pair of plasma headphones.
Something that will be the one and only main headphone, the one and only transportable headphone, and the one and only minimal portable headphone. The latter looks like a toss-up between the E500 and the ES2, so I may end up keeping both. The rest? Um, it's now down to:
Stax Omega II and Lambda Pro, Sennheiser HE60, Koss ESP-950, Grado PS-1, Audio-Technica ATH-AD2000, Fostex T50 (the old one, not the RP), Beyerdynamic DT880, AKG K1000 and K340... oh, to hell with it, I'll toss in the HE90 too, even though it's a bit out of the budget, especially if I want to have enough to mod that S2000 I'll be getting.