I received my Massdrop Plus today, here are some brief impressions!
The included package of case, tips, cable and IEM cleaning tool is quite good, the case especially is a nice size for portable use and will protect the earphones better than leather equivalents. The IEM's ergonomics are superb as others have said, and feel like they were made especially for my ears. My two gripes there are that the IEM sockets are recessed to such a large extent that some of my 2pin cables won't fit, and the nozzles are quite thick and short. They are terrifically comfortable though, and isolation is brilliant.
Regarding sound, they are tuned to be fairly non-offensive on any given frequency with no annoying peaks, yet detail levels are good and it feels like aside from the very highest frequencies nothing is missing. The sound is fairly spacious and very non-fatiguing, so I get the feeling being able to listen to music for long periods without any annoying ergonomics or sound characteristics will be their greatest quality.
Compared with my U8s with M15 modules, they do lack quite a lot of bottom end impact, the soundstage is good but not quite as wide and noticeably slimmer in depth, and they don't scale nearly as well with my AK380 & ALO CDM combo. The differences between the two IEMs are much less magnified through my AK70 MKII.
Overall I'm quite happy with the Massdrop Plus. For $300 I would not call them a bargain, but do think they're a very good safe purchase for the majority of audiophiles as its hard to imagine many people disliking their sonic signature or excellent ergonomics. A balanced cable included in the box with a 3.5mm adapter would be ideal, but I think a Massdrop Plus and AK70 or equivalent mid-range DAP would ably satisfy most people. To get the most out of them I would suggest changing the tips (I'm using JVC Spiral Dots which offer maximum clarity, Spinfits are also quite good) and upgrading to an aftermarket cable as I suspect a copper cable like the Effect Audio Ares II would help fill in their bottom end quite nicely.