#PLEASE READ THE EDITS AT THE BOTTOM#
I agree with the majority of positive comments on here, so I'm not going to reiterate them all. But I want to point out that this game is crippled by the checkpoints not being saved when you exit the game. I spent a significant amount of time getting the first 4 keys on stage 2 and then got stuck on my way to get the last one. I spend quite a bit of time on it, and then it started getting late and I just wanted to switch it off and try again from the checkpoint some other time, but I knew after making that mistake previously that it doesn't save the checkpoints...so I kept on playing.
Anyway, I ended up turning it off, and it's going to be hard to bring myself to go to all the trouble I already went through knowing that there's a bit I struggle with coming up. I'm sure I'll have another crack at it some time...
It's not the 90's anymore. I mean, it's cool to have the uber hardcore mode for people who want the bragging rights, but if you're gonna put checkpoints in the game, make it so they save when you turn the game off.
Even if I never play it again, it was worth the 94c just to enjoy the gameplay for a couple of hours, hence why I recommend it. If the checkpoints saved, I'd say it was probably well and truly worth the full $5 (assuming the rest of the game is as good as the first couple of levels).
EDIT: (I had another crack at level 2 after a good night's sleep and managed to get through it pretty quickly. It's a really outstanding game, but I still find the fact that it doesn't save the checkpoints both frustrating and a baffling design choice.)
EDIT2: After a few playthroughs it becomes easy to finish every level. Getting stars is more difficult, but once you've familiarised yourself with each level, it's easy to estimate how long it will take to play the level and decide if you have time to play. The play times are reasonably short, so even with a busy lifestyle it's no problem to set aside a few minutes to have a crack at getting more stars on a level. My only advice is to make sure you set aside plenty of time to finish the levels the first time you play them. The game is awesomely addictive, controls are smooth and responsive, and despite the somewhat complex mechanics for a platformer, it's very intuitive. The visuals are stunning, and the soundtrack is nice.
tl;dr: great game but the fact that checkpoints are lost when the game is closed is frustrating when you're first learning the levels.