So I beat the game a few hours ago. Here are my final thoughts:
Essentially, its Paper Mario without the creative characters, story, art design, move set, level design (To an extent), and RPG system. All of that stuff is missed greatly. However, once I accepted that the game is NOT an RPG, but rather an action adventure title with turn based combat, I was able to find enjoyment is Paper Mario: Sticker Star. It *is* a good game.
The sticker concept is alright. I just wish there was more to it. Half of the stickers are standard jump or hammer moves. Only a few are really creative. And they all control nearly exactly the same, with little variation. More depth here would have been appreciated. In terms of combat, I wish you could do more than just block. There are defensive stickers, but none of them last more than one turn. They were however fun to use. The slot machine mechanic was interesting, but leaving the number of stickers you can used mostly up to luck is slightly cheap. Granted, being able to pay to slow the machine down was a nice touch.
Enemy variety was also lacking, but this is due to Miyamoto's request to only use standard Mario characters. An odd request. Boss battles suffered greatly due to this. I will say as a side note, there is something very satisfying about collecting shiny stickers, and better yet, BIG shiny stickers. Battles were easy, but definitely fun. Only occasionally would I go out of my way to avoid battles.
Level design was surprisingly great, but the world design was not nearly as creative as in TTYD. Standard grass level, ice level, fire level, sand level. The two forest levels were highlights in terms of asthetics. Graphically the game shines - they really took the paper concept to a whole new level. I just wish artistcally the game matched its graphical prowess. The level design itself is not nearly as creative as TTYD either, but there were still some very clever moments. World 3 and the Boo Mansion level were highlights. The fact that the game was not strictly linear was good, and I liked the world map. Very Super Mario World esque.
The missing story is perhaps my biggest disappointment. Yes, Super Paper Mario had too much text. but to remove the story and side characters entirely? What? Bowser does not say even one line in this game. What a disappointment - it is in the Mario RPGs where Bowser has truly shined! His personality was so endearing in the Mario & Luigi games. And replacing the side character with Kertsi (Or however you spell her name)? Bad idea. She isn't as bad as Phi from Skyward Sword, but she was pretty annoying. The side characters from TTYD were much better. Thankfully the game retains its humor in the few cutscenes that it has.
The paperization of the world was a pretty neat idea. Led to some interesting puzzles. Didn't mind this gameplay mechanic at all.
Finally, the thing stickers. What an awfully implemented idea. Having them required for some segments of the game/boss fights was so stupid. They are hidden randomly in the world and the game never even hints at which one you need. Awful game design. I would say they should have just been uber-powerful stickers, but the game is so easy they are almost never needed. This should have been cut.
I didn't hate Sticker Star. It may sound like I did, but it was pretty fun actually. A solid 7 out of 10. Maybe even a little higher than that. It just isn't what I wanted, and I do hope they go back to the standard Paper Mario formula. As it stands though, it was a fun adventure game that I am glad I played through.