I love it, love it, love it. I've got 2 UAD's in one of my systems, and one in another that also has a Powercore in it. It will run great with Vegas. You'll use a DX wrapper, but it doesn't affect the latency. It should have its own IRQ.
Did you get the Cambridge package too?
It's a Universal Audio card that Mackie used to distribute. It provides hardware processing power so that the CPU isn't taxed with plug in use. Not cheap, but if you need/want better plug in quality, and you use a fair number of plug ins....it's well worth it. http://www.uaudio.com/
I bought my very first uad1 card when it first came out in the market a couple of years ago. Bought my second card when it was distributed by Mackie. Now I have 3 cards in my DAW and so far it hasn't acted up yet.
The quality of the plugins is to die for. You get the classic LA-2A, 1176LN, Fairchild compressors, the famed Pultec EQ and the Cambridge EQ. It used to be that the LA2A and 1176LN was included in the original bundle for the card but now it has to be purchased separate (correct me if i'm wrong). Anyway, the drivers is very stable. I don't use it in Vegas that much though, but it runs great in Nuendo.