I'm now far enough into playing Solasta that I can provide a first report. Personally, I'm loving playing this game. It's finally a game that sincerely scratches my D&D itch. I've also come to appreciate 5e a whole lot more because of this game. I think I will always like 3.5e the most, just because that was my personal prime D&D-playing years edition. But 5e is definitely second-best. The game is extremely faithful to 5e rules, and even such things as held actions and reactions are done beautifully. For a TB game, combat goes by pretty quickly. You have a good amount of options available to you in each turn of combat. The tutorial explains everything very well. The game includes character backgrounds that actually matter, and passive skills and spellcasting outside of combat are used extensively. Verticality and movement in 3D is awesome, including flying, spider climbing, etc. And yes, TA did this first. Larian copied TA for BG3. All in all, a truely delightful gem of a game.
For negatives, a very superficial one would of course be that the graphics and character models are not very fancy and sometimes look a bit odd. For some people this may be a big issue. For me, I couldn't care less. It is good enough. The voice acting is fine, though both written and spoken lines could use some more polish in places.
The main criticisms I'd offer are party size of only four, no multi-classing, level cap not all the way up to 20, and the game needing more content to explore. For the first issue, this may be the one game where this is okay, because they often attach critical NPCs to the party for certain quests. Early in the game we even get two such NPCs attached, effectively forming a party of six. As for the other three issues, I feel they all will become moot after we get the next DLC or two. TA's approach for this game appears to be to provide the core game plus a complete campaign first, and then release new DLCs every so often with a completely new, standalone, full-sized campaign. The DLC they're working on for a March release is exactly such a DLC. So TA seems to be doing what NwN was originally supposed to be, with TA's terminology being "campaign" in place of "module." You also have available to play user-created campaigns made with the "Dungeon Maker" toolset they have created and included with the core game. These are available in Steam Workshop and can be very easily added to your game.
More to come.