Can't speak out of experience (waiting for my 2box). There are now a couple of threads here about loose wires of the piezo. You should be able to find it.
But keep in mind that there always will be persons with problems. And it fairly quiet of real problems. MK2 seems much more improved, and i'm suspect every batch they become better. In case of problems there is good support of 2box. Using the 2box at live gigs is still debatable.
Just my 2 cents.
I am not a really hard hitter, more varied depending on the music, but I have used my MKI 2Box live many times for rock stuff, it has travelled far and in the 18 months or so of owning it, I have had very few issues. Bass drum sensor failed after a very long trip away and many gigs, but that was the MKI bass drum. The distributor picked up the drum, converted it to MKII version and it has been perfect ever since. Another issue I had was the snare pad rim rubber degraded after a year, and I had to replace the rim. Again the distributor sent me spares free of charge. The pads and module are very strong, and the new MKII rack is far stronger than the MKI version I have.
Yes, the wiring on some pads has come loose, and I do think they could impove that (I have mentioned it several times on the forum, because it annoys me - such a small detail that could make a large difference to failure rates) by improving the jack housing so the wiring isn't so exposed when opening the pad to change heads. The soldered wires need to have a stronger connection to their jacks. This can be improved if you aren't afraid of a soldering iron of course!
The cymbal triggering is good all round but the bell is not quite as responsive as the rest of the cymbal surface - its not too bad really and I don't notice it any more - we hope its fixed in a future software update.
All in all the newer MKII kit is far sturdier than the first as regards the rack and better snare stand and MKII bass drum, and the software continues to evolve and improve.
At the end of the day, I had Roland before the 2Box, and I would not go back. Because aside from the small issues I listed above, this kit is a blast to play. The 2Box is, to be blunt, simply a more expressive instrument than Roland TD-9 or TD-12 imo. Remember, you are talking 24-bit sample quality, with enough layers to make your drums sound far more real and convincing and round robin to eliminate machine gunning (another awful Roland trait). When you hear a TD-9 or TD-12, you can tell its an electronic kit. When you hear the 2Box in a mix with good samples, it is very difficult to tell.
So, 2Box has better sounds, and feels more 'human' and natural than v-drums. You can also increase SD capacity up to 32GB, which is tons. The module is simple and has far less effects and tricks than Roland modules do, but it does quality drum sounds far better. And of course its only as good as the samples you use. In short its a great instrument with a great feel and a reasonable price. In its price bracket the 2Box is still king imo.
