Full disclosure: I haven't finished the game yet, I've played about three hours so far. I'll keep my impressions spoiler free.
Bloody hell this game looks good. Astonishingly pretty. I thought Bastion was intentionally a bit slapdash in how objects and environment geometry were layered on top of the world while Transistor is slick and elegant as hell in contrast. I don't know how I feel about the story. There are so many different themes, some of them only gleaned through subtle hints, that I can barely wrap my mind around each one individually. It's intentionally oblique in a way that Bastion wasn't. Bastion obfuscated the point quite a bit but it did so you could infer aspects of the Calamity's effect on the world and what life was like beforehand. This feels more like a mystery, and it definitely has me hooked but I haven't quite figured out why.
The combat mechanics and systems are crazy deep compared to what I expected. There are so many possibilities in terms of combining the different functions. I generally like to do a lot of damage but it hasn't been serving me too well now I've activated some of the limiters. I'm barely scraping past most encounters despite having a reasonably good grasp of the mechanics. It's really satisfying to take out a room of dudes with a couple of well-placed, complementary moves.
Overall, I'm so wrapped in the game that it's hard to form a full opinion yet but what I've seen I've mostly loved.
How are you finding Supergiant's latest?
EDIT: Finished the game today. I loved the gameplay, absolutely adored it. Didn't run into the problems people had with abusing certain Functions to break the back half of the game. The final cutscene did manage to give the story the emotional punch I felt it was lacking but overall too many of the character's motivations were left unexplained. I didn't fully understand why the antagonists were doing what they were doing for most of the game and even by the end I only felt I had 50% of the story down. Also I didn't like how the talking sword was written. Some of his comments felt like they were superfluous, doing exactly the thing that Bastion smartly avoided which was narrating the moment-to-moment combat. I also thought the menu where you change all your functions sucks because you have to uninstall them from that menu and then go in and reassign them in the sub-menu. It looked pretty but annoyed me no end. I also had the freezing issue on the PC which sucked considering how intoxicating the atmosphere can be and how easily that was broken by a fat pause during combat.
Overall, the game isn't nearly a close to my heart as Bastion but I still had a good time with it enough to want to play through it again. Bastion is one my favourite games of all time though, so I had high expectations going in.