Plot is cliched, character types are ones we've all seen before, and the chapters tend to all follow the same basic formula (especially in the beginning and middle volumes); but even so I still found it entertaining enough to keep reading and was ultimately rewarded for my perseverance.
As noted, the biggest problem the series has is that for the first five volumes or so, almost every chapter seems to follow the same basic guidelines: introduce monster of the week, gang is threatened by said monster, gang gets the stuffing beat out of them until Tsukune pulls the rosary off Moka and her alter ego appears to save the day; wash, rinse, repeat.
The story takes on a different direction during the middle and later volumes, one that touches on some interesting themes, but they don't really go anywhere with it, and in all honesty I found this arc even less entertaining than the episodic ones we were originally given.
All is not lost though, as the last few volumes really improve drastically in every way possible. The artwork gets noticeably better, the stories are much more entertaining (even though there is still some of the monster-of-the-week stuff, it's less pronounced, and doesn't seem as formulaic when it is there), and there seems to be more of a focus on the characters and their relations which had been previously overshadowed by the plot. Much better; so much in fact that it brings the whole series up a couple of points in the rating.
So all in all, it's a decent read. It had some promise starting out that never quite got realized until the final couple of volumes, but that redemption gives me some hope that the second season will pick up with the same momentum that this one ended with.