At least in the UK, Sennheiser paid for my MTW return - I did however have to go directly to Sennheiser customer support.
The shop support (which is Digital River) were TERRIBLE. They essentially replied once saying "oh hey we don't deal with technical issues, contact Support", even though I specifically said I wanted to return the item. I replied saying I had clearly requested a return and they didn't even reply to that.
I had to contact Sennheiser Customer Service directly, and got a really helpful agent who expedited the return request. However I'm still waiting on a refund...so if you can buy from Amazon/some other store with a good return policy, I'd go there tbh, no need for this headache.
As a lengthy aside, finally got my MW07s - unfortunately it's been far too long since I returned the MTWs, so my comparison by memory is probably really fuzzy. One thing I do remember is that I got the MTWs on the same day as the Enacfire E18 (chifi, but decent) and remember wondering if the price difference was really worth that much. By contrast, swapping from the same E18s to the MW07 was like a little shock at how much better they were.
I may just prefer the MW07 sound signature though. I also agree with previous posts - their SQ is not really going to replace a good pair of in-ears of even half the price, but the convenience really really makes up for it. Lack of microphonics and cable snag is huge for me. Still testing battery life, but I think I listen at a relatively low 50-60%ish volume, so might get the full 3.5.
Usability is much better than the MTWs, at least so far. No issues with them continuing to play when placed in the case, case is just a tiny bit slimmer which actually helps alot, and they pair with both a PC and Android phone, reconnect with both instantly and swap between both seamlessly. This was annoying with the MTWs, you essentially have to repair each time (Go into pairing mode, then connect in the device settings)
They are COMFORTABLE, better than any other in-ear I've used, except maybe the Bose StayHear+ tips, which aren't really in-ear and have terrible isolation. They definitely sit much, much better than the MTW. Occasionally I would feel like the MTW might fall out (they wouldn't, but just had a weighty feeling as if the center of gravity wanted to get out of my conchla) The MTW also stick out quite a bit (was called a Cyberman more than once, for any Doctor Who fans out there...) and would often get stuck and fall out when removing sweaters/jackets. MW07s do not have that issue, they sit much more flush, and the wingtips help keep them very secure.
MW07s are also TINY. I didn't quite appreciate how small they are till I opened the case - they're much smaller in person than review pictures suggest. Also much smaller than the MTWs, and at least for me, are much less fatiguing to wear for longer periods.
Only gripes while I'm still in this honeymoon period are that the case is so beautiful that I have to use the soft case to carry it around in, and I keep looking at all the other colour options wondering if I love the one I have or would be happier with another one....They are really gorgeously designed IMO. Additionally, would really like a magnetic seating system - they haven't failed to charge, but it just doesn't feel as secure as a lock-in or magnetic system. The lid does push them down consistently, and is itself magnetic, and it may have been to accomodate the acoustic chamber.