Master of the Monster Lair has the concepts to make it a worthwhile title. Each of the individual parts work in theory, and mesh incredibly well - it's obvious that Global A put significant thought into how dungeon play should complement what's done in town. It's the fact that these individual parts aren't of particularly high quality and have very annoying features that makes Master of the Monster Lair a sub par title. Nothing in the game is completely broken, but on the opposite side of the coin, none of it is original or shines as an excellent feature.
For gamers who don't own a PSP or are in the younger echelon of RPG fans and want to get their creative juices flowing, Master of the Monster Lair might be a title to look at. Those who own a PSP, however, should skip over Master of the Monster Lair and try to find a copy of Dungeon Maker - it's almost the exact same game without the kiddy overtones and a superior battle system.