I fairly regularly ride WAB-ESX and MPR-ESX (that is Waterbury or Montpelier, VT to Essex Jct, VT).
The fare is $8.50 and $10, respectively, and if I plan far enough in advance I can take my NARP discount off that. Waterbury is about 30 minutes and Montpelier is about 45, I think.
What I end up doing is taking a commuter bus down after work and riding Amtrak back (then taking a bus home from the station). There's a fantastic brewpub in Waterbury, so occasionally I and a few friends will take the bus down, have dinner and a few beers, then hop on the train back to Burlington. It's a lot of fun to do and a great excuse for a train ride.
I'll travel to Montpelier occasionally for various events, or occasionally to do some work for some people down there and use the bus/train combination also.
Riding within the state is becoming increasingly popular, as this is the second year in a row that there's a $12 for anywhere in VT deal.