My opinion is that since fixed gear bikes are more difficult to accelerate, light wheels are even more important and more fun than on geared bikes. I have two fixed gear bikes, one with Phil hubs and Velocity Deep V's, the other 1st gen Dura Ace front hub, and a Nashbar flip flop rear on Mavic Open Pro rims. The Phil Wood hubs and Deep Vs are gathering dust since the lighter Open Pro wheels ride so nicely.

I'd love to have some even lighter wheels on a fixed gear.

You can buy a pre built fixed gear cheaper than you can build one, but you may not love it as much.