1. How do you feel about Exalted's splats in a general sense, both as a game element and storytelling device?
Personally, I like it, because it let you play with different heroic archetypes and let them have tools abbilities appropriate to that archetype. It also let me as a Storyteller setup NPCs with wildly varying power sets but with my players still having some idea what to expect out of any given NPC. ITs also somewhat interesting to see how those abilities contrast and clash at times, particularly in mixed groups.
2. Which splats do you feel work best, and why?
Alchemicals are my favorite splat for a multitude of reasons: a very neat world connected to them, steampunk/robotic powerset, the whole idea of them being heroes for the people, as opposed to rulers of. It makes for a nice contrast to the other Exalt types.
Dragon Blooded, have always stood well. Their general themes of elemental super soliderdom and bonds of brotherhood have stood well, especially given the feuding nature between the different families/groups/clans of the Dragon Blooded. In a lot of ways I think they have the most story potential of any of the Exalt types, between the Realm, Lookshy, the returning Solars and Outcastes games. They have a lot of history to them in a way none of the other splats really do.
Solars work very well in their role as 'generic' heroes. Their themes and visuals work very well toward the shining hero of immense power, that may or may not be good, and their powers generally back it up. Similarly Abyssals work well as their dark mirrors, though execution has been lacking there. I admit I'm a bit of a sucker for light and dark mirror image symbolism though. I will admit that the caste distinctions are annoyingly vague at times, which is part of the reason I'm rather happy 3e tightened them up a bit so that you actually were more solidly good at something in theme for your Caste. That said, if you can get your hands on them the Caste Book series is great for getting a feel for each Caste (except Twilight. Twilight is terrible, but thankfully Twilights role as the smart guys of the group is fairly easy to grasp).
3. Which splats do you think don't work, and why?
Lunars. Oh god Luanrs. They just never had the solid thematic to back them up the other splats had, and have always been a bit of mess no one knew what to do with. Which is a shame, as shapeshifters are cool.
Sidereals, mostly because I've had to deal with their 2e iteration where their mechanics never really made them terribly great at the whole hidden master thing. The fact 2e never really tried to integrate it into the setting at all didn't really help, and the fact their main playground and toys (Yu-Shan and the Loom of Fate) were not particularly well fleshed out from a perspective of playing Sidereals made playing them difficult.
Infernals, oddly for much the same reason as Lunars. There a thematic mess, thanks to Chapters 1&2 being objectively shit, and Chapter 4 not much better. Their supposed to be corrupted Solars, and yet virtually none of their mechanics really engage with this, and the ones where they do cause problems: notably Castes locked to Solar ones are extraordinarily limiting when a major draw of the splat is add-a-yozi for a powerset, and Past Lives should really be an Abyssal power (memories of the pasts long dead coming back to temporarily take you over is rather more in theme for Abyssals with their whole focus on death). further, the fact they don't really have a defined role in the setting leads them to basically be 'Solars or Abyssals, but green' most of the time.
The Charms are fun though.