4 of the best special occasion dining options in Brattleboro are:

T.J. Buckleys - a "Chef's Menu" style restaurant located in an old restored train car.  Very small, reservations required.  Cash or Checks only.  Not inexpensive, but worth it.  Entrees are about $30ish.

Peter Havens - a Brattleboro favorite, friendly staff and consistently great food.  Larger than T.J. Buckleys, but reservations would still be reccommended here.  There is a small bar that you can sometimes walk into a seat at.  Entrees are about $25ish.

Alici's Bistro - the newest place on the list, has a martini bar downstairs and an outside deck (the only upscale place in Brattleboro with outdoor dining).  Reservations are a smart idea here as well, especially if you want to request an outdoor table in the summertime.  Entrees are about $22ish.

Capers Restaurant - small, intimate place with a consistent and interesting menu.  Can be noisy, but the food and service makes up for it.  Small as well, so make a reservation.  Entrees are about $22ish.

Brattleboro has a lot of great eateries, but these are the ones that come to mind for  "special occasion dining".