I was a huge fan of Harvest Moon 64, playing at friends' houses when I was a kid, and have been disappointed with the more recent Harvest Moon games I've tried. This is a different, slightly more complex game (what with the monster-taming and all), but it keeps the awesome spirit of Harvest Moon and, in many ways, improves on it.
The most annoying thing are the unskippable cutscenes, particularly the opening one. It'd take a lot for me to start a new file just because I know I'll have to sit through 5-10 minutes of cutscenes I can't skip (plus the unskippable tutorial stuff) just to get into the game. Additionally, unlike Harvest Moon in which you start with a full set of basic tools, here you have to be given each tool by a different person. There is no in-game guide or quest progression to give any indication who will give you the next tool, nor how to get them. It's frustrating, though not a big problem considering the wealth of information on various online wikis about the game.