Got a Legion beta invite, so I've been messing around on the beta servers for the last couple of days.
So far, Legion looks really promising. Looks like Blizzard has learned from their mistakes (Warlords of Draenor) and is now back to taking chances. Lots of cinematics in the opening sequence of the expansion. Won't go into spoilers, but major changes happen within the first two quests of the expansion storyline.
As for Druids, my focus has primarily been on Bear Dudu, because Feral just doesn't click with me, anymore. Unfortunately, Bears got shafted in Warlords of Draenor to the point where playing one is simultaneously the most annoying and most boring experience ever. Bears in Legion look pretty amazing right now. It's still the same boring rotation, minus Lacerate (Thrash stacks to 3 instead now), but the talents allow you to mix and match your playstyle. I, personally, am a huge fan of the talent Galactic Guardian
. Chance on damage (even damage over time) to launch a free Moonfire on the target. Get into an AOE situation, mash Thrash and watch the skies light up with laser beams everywhere.
And the artifact thing has won me over, primarily because it appears you can transmog any weapon to look like any other weapon now, so you're not restricted by the weapon type you're using, aside from one-handed or two-handed. And for Feral/Guardian Druids, wielding the artifact weapons come with a bonus, because the new bear and cat models look awesome. The Guardian weapon looks pretty sweet, too. Link to Imgur with pictures.