I hiked it in four days in mid June last year. Overall, it was a fun trip with a few friends. More road walking than one finds elsewhere but, northbound, that lessens after the first long day. The first day is long because of the limited choice of camping opportunities – either just past Monadnock or at about the eighteen (?) mile mark, just below Nelson. Lots if nice sections after that. The forest above Nelson and Pitcher Mountain’s tower and blueberry fields were especially good. The Sunapee area was nice too but we missed any views it offered because of rain and fog.
I’d recommend taking a water filter if you have one. A few of the water sources were a bit low and somewhat stagnant. I’ve since switched to Aqua Mira and am comfortable straining assorted floaties but I was glad I had the filter on that trip. Also, if there is still a detour at about the halfway point, be sure to follow it. We met some southbounders there who missed the detour at the north end and encountered a lengthy and very deep section of mud.
The MSG is different from the more rugged areas to the north but very appealing in its own way, and quite interesting if you take the time to read the guidebook. If you have been to Monadnock countless times and want to save a day, consider starting below Nelson.