Art: I think the cover speaks for itself. It looks nice, character designs are simple yet come off as quite memorable and in general the animation is doing its job perfectly fine for a simple slice of life.
Sound: Honestly love the opening song and in general all the tunes. The sound design is also nothing to scoff at.
Characters: they're all likeable but I don't think any of them are anywhere near fantastic. Dagashi Kashi works well because it is carried by its characters interactions and Hotaru's insanity, but if you look at the fine print none of the characters are amazing or even great. Kokonotsu, Saya and To each do a better job than your typical harem protagonist(no this isn't a harem anime), typical childhood lover/friend and typical annoying best friend. There is effort in making them stand out, and they do stand out, as in they're not as lame as most of what you can find, and each of them has personality and charm. It doesn't make them great. I liked all of them and would watch the anime again to see them again, but I will not remember any of them.
Enjoyment: To be very fair Dagashi Kashi is best enjoyed in small increments. Barfing the 12 episodes in one night would be the worst idea for a simple reason: the whole show relies on its characters and Hotaru's insanity as I said, and there isn't enough material there to fill 12 episodes with interesting content. So instead DK tends to stump around a bit and drag and repeat its architecture again and again. An episode starts, Hotaru will do or say something insane, it'll end up being about a sweet, and we'll have a ton of character interaction and trivia about the sweet. It's a fine system and there's nothing wrong with using it a lot, but DagaKa ONLY uses that, beyond this principle there is no plot and nothing really new ever happens. I think the Festival episode is the only one with something actually different.
Overall: I watched Dagashi Kashi in two parts, episode 1 to 7 then episode 8 to 12. I can say for sure that I stopped for a while after 7 simply because I was bored. A boredom which had disappeared by the time I came back to it some weeks later. If I had to state an overall feeling on Dagashi Kashi it would be that among then numerous comedies with commercial goals and plotless slices of life that I've watched, I think it's still on the higher tiers of quality. It's worth watching and it is fun, even if it does get tiring after the jokes have been seen a few too many times. Likeable and interesting characters go a long way, and even if Dagashi Kashi doesn't have much more than that except the obvious erotic undertones constantly thrown around, it's enough to make it enjoyable, if only slightly.
