It's been a couple of years since I've been, but I always found it worthwhile (UPA.) Similar to Summit crowd, in my estimation—working practitioners, not overly academic. More of a research and testing bent, but also folks interested in talking about interaction design, UXD, etc. I'd recommend you go if you can.

What's sad is that I live in the Baltimore/DC area - would take me about 2o mins to get to the UPA conference, yet I won't be going. Company would pay for IA b/c conference cost was cheaper than the UPA one (even though I wouldn't need a place to stay).

Look at the presentations. From what I can see, it looks to be good.