I poked around last week, and it seemed like a cool site with some nice features.
What turned me off the most was that I couldn't create an event without entering an address for it. I just wanted to refer to it as "Robert's house", which is all I need to get myself there. Even if I mark it "private", it's still a possible privacy leak. Plus in this case, I have no idea what the address actually is...I just know how to get there by car.
There were a couple other thing like that, I think, where it either wanted more information than I had or was willing to give, or was otherwise too strict for my tastes. Oh, maybe it didn't allow me to say "Robert and Alex will be there" without actually inviting them to the site. I forget.
Kevin