I tried taking a look at this on my Windows PC last night and their web site kept crashing browser windows, which wasn't very helpful. When I tried it on my MacBook Pro (which is what I'll probably be using since it has a camera) it sulked because it wants to run on Chrome, not Safari, but eventually let me access via Safari. It won't run on tablet computers or phones at all.
So far my impression is that it's cutesy crap. The user interface looks like a game for five year olds, and there appears to be no way to use it if you're blind or have trouble with coordination. You have to move little icons of a person around a map (by keyboard control only, no mouse or pad) to access anything, and it's painfully slow. The idea appears to be to force people to encounter each other socially by wandering around the map, not just click from one event to another, and I wouldn't mind if it was just there as an option, but having it as the only way to access things seems a little silly - if this is to work at all the social space between the event locations will have to be big, requiring a lot of movement to get from one event to another. For me it will be a problem - when I'm working on my main computer the laptop is on a shelf with the keyboard at roughly shoulder height, and trying to operate the keyboard gets physically painful after a couple of minutes. The touchpad is better, but that doesn't seem to be an option with Gather.Town
The largest event I can find on line that used it seems to have been around a hundred people (not sure how big Eastercon will be, probably a lot more) and they were using other interfaces for a lot of the organisational stuff such as panel scheduling. Given what I've seen of it I'm doubtful it will work very well as the only way to get around.
Does anyone have any experience of this other than their demo site? If so, what did you think of it?