I have a love hate relationship with wafer based bars. The highest rated candy on this site (the Kit Kat bar) is wafer based, and some of the lowest rated candy on this site is also wafer based bars. I think it's very easy to make a bad wafer bar, and very difficult to make a great one. The reason? It's all about why you're using the wafer.
Wafer is a cheap ingredient, most of it is actually free, because they’re filled with air. Wafer is a great way to pump air into your candy and claim it's an ingredient. That's not to say that wafers have nothing to offer. Wafers also offer a really nice texture to a bar, and a way to build layers while keeping a bar light (in a good way). I think the difference in wafer based bars is all based on the stinginess of the maker.
The folks at Kagi however have left me a little stumped. First of all this bar feels really, really light. It's very light and full of lots of air. The chocolate coating is also very thin, on a warm day you could probably take off the outer layer of chocolate with your warm fingers. These are two warning signs of a possibly cheap and crappy wafer based bar. The difference here is that the chocolate actually tasted pretty good, and the filling between the wafers was tasty as well.
This is a really rare occurrence, it's a wafer bar that I don't love, but I also don't hate it. If you see one at a reasonable price, and you're craving the crunch that only a wafer can give you, go for it. I wouldn't seek out this bar, but I didn't mind finishing the one I was eating.