Past gatherings have included all abilities from intermediates on up to expert.
The New England Gathering is rather informal in that there's not really a set itinerary, etc. So much of what we wind up skiing depends on the conditions, and -- in New England -- the conditions can vary widely from day-to-day. It's more about skiing with fellow EpicSki members than it is about "skiing every possible line in four days". We tend to wind up skiing something of everything though, from groomers, to bumps to trees. But we've had icy days in the past where we never left a groomer, and we've had powder days where we never saw a groomer. Nobody is ever pressured into skiing something that they don't want to try. i.e., there's always a way around and we will always wait up.
So, in essence, some ability to ski ungroomed terrain would help, but you don't have to be a bump / glade / powder skiing expert. My glade skiing prowess -- or rather, the lack thereof -- is well known and I run the gathering, so... If you have a willingness to try skiing some new terrain with some really cool people and you're able to ski in a manner such that you don't endanger anybody, you are welcome to come.
Thank you KevinF! I'm a solid intermediate skier who have only skied groomers and definitely plan on joining and meeting every one during the Gathering. I hope to improve before then.