My first though after watching this was, "Hey, it's Ninja Scroll, but done poorly!".
Basically, this is a typical monster/ninja movie, complete with the stock "emotionless hero" and loads of hideous beasts. Now that's all fine and dandy, except I consider things like plot and character development to be a bit more important than nasty monsters and bloody violence.
Almost everything about this movie ends up flat. The plot simply involves a samurai named Hikage searching for his missing friend who has disappeared. It's a fairly linear affair, rather predictable, and acts as an excuse to have the "hero" chop up various beasties. Unfortunately, since I didn't care about the hero, I didn't care about his actions. Emotionless ninja are fine as minor characters, but incredibly boring when focused on. I suppose if you're a horror junkie you might find some of the zombies, monsters, etc, appealing. There's a fair bit of blood and gore, which should appeal to action fans, but I found it rather unimpressive.
Visually, everything had a dull appearance, but this was probably done on purpose to help convey a sense of horror. The background art was generally pretty good, though, although the animation wasn't the greatest.
If you're looking for a good ninja movie, go rent Ninja Scroll. Curse of the Undead Yoma will probably just bore all but the most blood-thirsty action fans.