Very much worth it at that price.
As for what to expect... It plays pretty much how I expected an Elder Scrolls MMO to play. Similar to Oblivion and Skyrim, just with the usual limitations that are presented when going MMO.
The main strength ESO has over other MMOs, I've observed, is its quests. Quests are story-heavy and dialogue-heavy, and you can tell the designers tried hard to avoid resorting to generic WoW-style fetch quests.
I bought this as soon as it dropped again because of WoW burnout and I am so happy with my purchase. I don't get the general hate for the game since it really does feel like playing a TES game where there's occasionally other people. Love the classes, love the way the skill system works, love the way the game looks. The UI is kinda clunky (though you can mod it) in the same way Skyrim's UI is clunky (since it's Skyrim's UI with a few more menus).
The one thing I'm really enjoying though is that the game world feels legitimately huge like you would expect from the series. Like in a normal TES game I just find myself wandering a lot and actually feeling like I'm exploring the world instead of just going from objective to objective. The game rewards you for that too since there seems to be a fair amount of stuff off the main paths that doesn't get marked on your map until you get closer to it. I like stumbling on these mini quest lines or caves full of monsters or bandits and their leader.
To that end I keep wandering around taking screenshots. Last night I was near an erupting volcano:
With the game being structured like a TES game and not WoW those kinds of things are actually really refreshing too. There's mobs and NPCs in logical places and not just an endless stream of things to kill across the entire game world.
If you don't like MMOs it's still an MMO but if you enjoy the genre I think it's worth it for $12. Certainly getting my money's worth out of it already even if I don't end up playing it long term. Can't wait to try some of the group content and PVP though.