I've played... quite probably too much of this
I really love it. I've now played as four of the six classes available so far, taking all to level 4 but only finishing the EA with my rogue and fighter. I'll probably leave it there for now until there's more content added, and also I didn't really feel like playing as a cleric (my most yawnsome class in any RPG) or wizard, as I feel with the current level cap you're quite limited in terms of effectiveness.
First play was as a rogue, which I enjoyed, although I don't know if I'll main it when the full game comes out, as I enjoyed other classes more, and also I like Astarion so would like to keep him in the party.
Second play was as a ranger, which I really liked. Felt quite strong both in melee and ranged (I was mainly speccing for a melee build), and being able to call on a giant bear or spider from level 3 meant the group as a whole felt very strong. For this one I also played a drow, which opened up different conversation paths and made one group in particular act very differently towards you. It would be interesting to see more of that dynamic throughout the rest of the game.
Third play was as a tiefling warlock, and once you level up your eldritch blast with agonising blast and repelling blast, and can send enemies ragdolling around and flying off ledges, it was quite fun. It feels like you can build one to be pretty powerful, although I don't know if using EB as every attack would become a bit monotonous longer term to main one.
Final play was as a fighter. Usually a class I never pick because they always feel a bit vanilla-bland, but of the four I probably had the most fun here (maybe tied with ranger). First of all it meant I could kill La'Zel when you find her the second time and loot her armour

. But when I found trinkets that allowed me to gain 2 AC as a bonus action and misty step, I basically became a juggernaut capable of teleporting around the battlefield, hardly ever took damage in combat (which if you pick the right feat means getting a reaction attack against any enemy that misses you in melee), and could kill most enemies in one or two hits (though difficulty did noticeably go up in the underdark... though even then I was the main damage dealer with insane survivability). Even though it was my fourth and (for now) final run, it was the one that most left me wishing I could continue as this character.
I didn't even need any fancy strategies to take down the minotaurs or hook horrors, just kept hammering at them until they went down. With the former, the fight was even easier when I saw they're vulnerable to bludgeoning damage, I switched from my greatsword to my 2h maul and was now doing circa 20-30 damage per hit rather than 1-10.