I should add I've only played yesterday evening and a few hours today, though I made several characters and one of them ("Stargelman") got quite a few hours of play. My experience is limited, but enough for a first impression, I think.
The good:
Character generation is fun, so you get fun right at the beginning. You can customize your character in many ways, and it's very easy to make your character very pretty or butt-ugly. I always thought that to be impossible in Oblivion, I was never happy with the way my character would look. Not so in ESO. You can easily get the look you're aiming for, and the options for customization are good and plenty.
Speaking of good and plenty, that's also true for the world. It's huge and it's pretty-looking. No matter in what part of Tamriel you start, it all looks pretty, and all three starting locations have their own unique look. There are forests, beaches, hills, mountains and of course all kinds of critters both friendly and fierce. Deer seem to be on tranqs as they no longer run away. You can also opt to chase butterflies or fireflies (called lamp bugs) for hours, if that floats your boat.
The bad:
Don't expect any of your choices to matter, save the decision what faction you wish to belong to. That, after all, determines your starting location. Anything else? Doesn't matter. You can pick a class, but what difference that makes in the end is a mystery to me. Everyone gets skills based on stamina and magicka, it's just different but very similar-working skills. I haven't seen any class-based quest differences at all. So why even pick a class? Why even have them?
As for dialog... that's never been a strength of TES games, I guess. But it's actually worse in ESO than it is in other games, for one simple reason. In the main series games, you were automatically assumed to be the hero, the guy (or gal) who saves the entire universe and then some. So when people approached you and said "I've heard good things of you. Can you please save my entire family while risiking your immortal soul, and all of that for free?" you'd think, "sure, I am THE hero, after all". In ESO, it's harder to pretend to be The Chosen One when you're literally drowning in crowds of heroes and you have to search high and low for something to kill because as soon as anything spawns, someone else will be there and mow it down.
Still, in other MMOs, you get to at least pick and act a certain role. You can play a guy who's just in it for the money, a classical hero or a guy who's just a total bastard for the heck of it. The dialog options in, say SWTOR allow to act that out and it does make a difference. Sometimes just in subtle ways like an alignment shirt, but still. Nothing like that I've seen in ESO.
I won't moan about bugs because what I played was a beta, so you'd expect some rough edges. That's after all what a beta is for. There still seem to be plenty left, but then, it's got "Elder Scrolls" in the name

The interface, in my opinion, still needs a lot of work until it's up to par in terms of usability and features. Five quick slots? FIVE? I've got 50 in SWTOR

In summary:
Good-looking, but kind of soulless. Kind of yadda yadda. I can't see myself spending money on that or playing it for prolonged times. Someone said good content would only come at a higher level (they said something like level 45) but why would I stick with it that long if I didn't really enjoy it? Or pay big bucks for it, for that matter? If they make it free-to-play later, I might give it a second look, but I'll probably spend most of my time in character generation.