My daughter and I used the Boston T to travel all around the city. We bought a 7 day Charlie card, for $15, which allowed us unlimited usage on the T, buses and harbor ferries. With single trips costing $1.70 each, it was a worthwhile investment for our 5 day visit.
The subway cars were generally clean and air conditioned. Except for one trip during rush hour, we usually managed to get a seat. But waiting for the train (actually more like a trolley) was another experience. We were on the green 'E' line and when we were heading back to the hotel, it was not unusual for a couple of 'B', 'C' and 'D' green line trains to come through the station before finally getting an 'E'. When heading into the city, on a line that only ran the E, the wait could be 10 minutes or more.
A couple of stations were in need of a good cleaning. The wheels on the trolleys didn't always perfectly match the curves they needed to make and the screeching of the wheels against the rails was ear-splitting at times. Truthfully, I found the 'T' a necessary evil. It was definitely easy to use and generally convenient, with easy to read maps everywhere. But there were times I would rather have taken a bus ... if only I could have found a map of the bus routes.