The capsules have a communicating partition between the two berths on the same level if unlocked by both parties, so interaction between consenting travelling companions is possible. The idea's major attraction is security, so you can keep your belongings locked up and safe while you visit the bathroom or buffet car, and protect yourself and your stuff while asleep during the night. There are lockers for each berth in the central pillar behind the ladder and a large shelf above the side corridor accessible from each upper pod. Classic couchettes, which I have happily used many times, do not provide anything like this level of individual security. I would certainly like to sample the capsule experience if I ever have the opportunity.
Yes indeed - as I said, if the capsules are a sort of "super couchette", with more privacy (and more claustrophobia!), for a bit more money, then fine. (Especially, if the old cheaper couchette bunks still exist too.)
What alarms me is if the capsules are an excuse to do away with the existing (non-deluxe, non-en-suite) standard sleepers, which are the right combination of facility/comfort/price for many of us. I definitely see them [the new capsules] as a more private equivalent to the couchettes; they don't seem to me to be anything like normal sleeper berth, and hence shouldn't be an excuse/reason to deprive people of the latter unless they can afford to pay more than hitherto. As it is, the existing sleepers are an important component of my ability to get around Europe conveniently and affordably; I fear I might be priced out of them, indirectly on account of these new capsules.
(The Euro35 extra for the compulsory higher-grade sleepers - mentioned above - is a significant proportional increase on the existing sleeper price.)