Listening to mine right now (did not buy them through the drop, as I didn't know Massdrop existed until long after the drop). If they ever come back, there are a number of reasons to like or dislike them, but "gimmicky" seems unfair. Yes, the bass is adjustable, but it isn't a simple "boost" on/off, and it is completely passive.
They are quite comfortable (I've gone 6+ hours with them at one sitting more than once) and while the fixed cable might be problematic, it accommodates the variable bass and I suspect this would be more difficult to implement with detachable cables. As to replacing the cable, if necessary, there is a YouTube video demonstrating how easy it is to do (and the cable itself is not all that expensive--certainly less than many aftermarket cables for headphones and other audio gear).
Are they the best headphones I've ever heard? Of course not. But (especially at the low price I paid for the floor demo model) they are quite nice and in situations where closed-back phones are required (as is often the case for me in libraries or to "tune out" outside distractions at home), only headphones several hundred dollars more expensive (than what I paid, not necessarily retail) offered equal, or better, performance. And with the very eclectic variety of music I listen to (from 70s prog rock, to Ella Fitzgerald, to obscure 20th century classical quartets, to bluegrass...), the variable bass tuning is nice to have.
I am looking forward to my first pair of open-back Sennheisers (the 58X that I ordered for a June delivery) to compare. Perhaps I'll no longer be impressed with my 630VBs after that (they will have cost me about the same after conversion of US to CDN dollars), though I suspect I will like each for different purposes.