One thing I have to say about Parhelia: it will be very, very expensive. And if you need 3 (!) monitors to utilize all of its capabilities,... well... I'd rather go with a next gen Radeon, I think it will be cheaper.
There will be more than one version, so I'm sure they will have one that is less expensive than the tripple head card. Ultimately all top end hardware tends to be pricey.
Not bad. But I think you would get a sore neck looking left and right.
I'll say, while the Idea of three monitors working as one is an innovative one, it's not very logical. Picture distortion will be the major drawback.