Some of the early units had pressure issues, but that shouldn't be a problem for current examples. I'd be leery of buying from someone else, used, however.
I've used paperless systems before, but to be honest, even with two of them on board, I've had both fail at less than ideal times. The most notable was approaching Miami during a busy time, IMC with convective weather, and getting assigned to an arrival about the time the units failed. One locked up and couldn't be reset, and less than a minute later, the other failed.
We're getting them in our aircraft again; I flew the first one to have them hard-mounted in place a few days ago. While they're handy, I still prefer paper. I've never had a paper chart lock up on me or fail. Paper's a pain to update, and pages can tear, but batteries don't go out on paper, they can be read in all kinds of lighting, they easily clip to a kneeboard or a control yoke, and I like paper.
If you decide to try paperless, I'd strongly encourage you to at least print out the charts you intend to use, before you fly, as a backup, and for the first year or so continue to carry your paper along.