Shortly before Christmas I was one of two PCs playing through the introductory D&D 5th edition starter box adventure, The Lost Mine of Phandelver. It was a great evening, but I was struck by how this new edition lulls you into a false sense of security. You think that with so many hit points and abilities you are practically invincible and can take on all comers. In fact the opposite is the case because 5th edition monsters pack a heck of a punch; we effectively had two TPKs in the session because we kept stumbling into deadly scenarios thanks to our attitude of blithe self-confidence. Rookie players used to Basic D&D or OD&D, take note: you may have a lot of hit points and spells but that won't matter when bugbears do 2d8+2 damage per hit.
This is certainly a big improvement on 3rd and 4th edition, though you have to wonder if there isn't a bit of a red queen syndrome going on: 5th edition PCs, it seems to me after running and playing in about a dozen sessions, are about as fragile as Basic D&D ones. Everything has been amped up in turns of hit points and healing, but all the threats have been hugely boosted as well. The game works and is probably objectively the best version of D&D since the Rules Cyclopedia, but the feel is also quite similar to that iteration because the threat levels (and also the pure vanilla tonal palette) are effectively the same - it's as though we've gone through 20 years of change to end up in exactly the same position we were in back then. This is no bad thing, but perhaps a cautionary tale about the value of change in itself?