Prices to fly in and out of Logan vary wildly depending on where you are coming from, and which airline you're using; it's worth shopping around. (I mostly fly JetBlue and Southwest these days.) But keep in mind, we're getting close enough in that fares are going up rapidly.
While I agree about the Red Line, keep in mind that we're in the middle of the city, so Lyft, Uber and suchlike work fine if your hotel isn't right by the subway.
(The only one moderately nearby that I've stayed at is the Hyatt Regency, which was home to the Arisia science fiction convention for a number of years. It's entirely decent, but a modest hike from the Broad.)
70 here in Boston as well, but we're back to normal temps tomorrow. Mid-March is likely to be upper-40s / lower-50s (F), but that's easily +/- 20F. The only rule of Boston weather is that there are no rules...
@adelbertc Virgin is by far my favorite when it's an option -- pretty much the only airline I like. I always fly it to Britain when I can. JetBlue is generally fine. I despise Delta with a burning passion (although at this point I probably dislike American even more). Haven't flown Alaskan.
Virgin/Alaska canceled my last flight and didn't notify anyone on it. I found out on my way to the airport. They moved me from a (nice) Virgin plane to a (Wright Brothers Era) Alaska plane several hours later.
Agreed about JetBlue for the SFO <-> BOS route. They have lovely, well-outfitted A321s. (Someday I will splurge on the Mint seats -- basically first class, not something I had associated with JetBlue.)