We realize that Facebook is a dominant competitor in this market space and a lot of people use it for creating events, but there are still some people we've talked to who aren't entirely happy with it, as well as some market segments out there that aren't avid Facebook users.

How big is the addressable market? What you just described sounds pretty small.

"...still some people we've talked to who aren't entirely happy with it" This sounds like people that are slightly annoyed, and not really displeased enough to switch over to something else.

For my last party invite, I tried using facebook but a lot of people balked at it. Pretty sure the reason was that it forces you to think that you need to sign up/log in and people just want to have an easy access to event time/address, and a yes/no button to rsvp.

I just created a test on anyvite and it was super easy and common-sense. Definitely preferrable to facebook in my opinion. Two comments though:

1. RSVP dropdown is smallish/hard to notice. 2. Background images stretch in an ugly way, at least on my work IE 1024 x 768.

Otherwise, a great site!

This really depends on your specific group of friends.

For example, most of my friends do not use Facebook.

But all of my friends use email.