Mad River is hard to tolerate unless you plan on being incredibly drunk the whole time you are there.
It is beyond packed, which is very uncomfortable. It takes forever to walk from one side of the bar to the other. Drunken people come up to you and dance with you and are often too coherent to leave you alone when you ask. There are bottles and cans all over the floor, and everything is sticky.
Mad River seems mostly to attract like 21-year-olds and people who wish they were still 21.
For a better night of drinking and dancing, head next door to Brew Pub for some good beer, a larger space, and an older crowd.