I got Chibi Robo on Wed., and I've already put about 4.5 hours into it. This game is fun in an Animal Crossing meets Majora's Mask sort of way, but without the irritating features of either of those. The game exudes an incredible amount of charm with endearing characters and scripted events that pop up when you least expect them.
Exploration is the name of the game and those who get the most out of the Zelda games when exploring every nook and cranny are in for a treat. IGN's review suggests that the game becomes harder/more frustrating later on, but I haven't reached that point yet, so I can't comment on that. What I do know is that this game is very fun, very addicting, and so far, very worth it.