I read this after watching the anime series, and I must say, the animated version is far superior. However, that's not to say that the manga is not worth reading. I'm not a huge fan of the harem genre, but they tend to be quite hilarious, and this one, especially so. I like the idea behind the story; its one that I've never encountered before, and its certainly something that I wouldn't have been able to come up with; +points for being creative.
Other users have commented that there are a lot of 'wacky' situations, but that is what gives this series a unique charm. This is quite possibly the most hilarious series I have ever read; the only other competitor would be..."Sexy Commando Gaiden: Sugoiyo! Masaru-san" (which I highly recommend). The difference between "Seto..." and "Sexy Commando..." is that the former focuses purely on nonsense. Seto no Hanayome is a mix of elements, with a love triangle, school life, and a heavy dose of comedy.
I agree that things start to slow down and become a more typical 'love-triangle shounen manga' (hence, points off), and things can get a bit bumpy, but it was not enough to prevent me from completing the series. As is typical of the harem genre, some rather irritating characters appear later on, one of which I continued to dislike throughout the series, but most of the characters had something to contribute to the story and the lulz.
If you're looking for lulz, and this series doesn't seem to cut it for you....you might just have a problem.