There are quite a few things to like here. The graphics are classic cartoony 2D done very well, the setting is great, and the humour is funny, although there are a few lame points, the UI works well, even the plot is fun to follow near the end. Most importantly, although this ones hardly a nose bleeder, is that the game doesn't spoon-feed you everything. Granted this has always been a significant part of the adventure game genre, but games of today have made me wary. This is not to say the game leaves you hanging, it just tells you what to do in subtle was.
As for bad things...there isn't really anything outstanding. The game is maybe a bit short, but given the genre I'll let that slide. Perhaps the biggest flaw is that there are simply to few intractable flavor items and actual quest items. This is something I'd normally think of as an indie dev issue, but not really like the other elements in the game suffer from this.
Deponia is a game filled with soul that any fan of point'n'click genre should try out. It's not as good as the classics but who says it has to be?