I'm not sure how to review eversion. It's an interesting short game with an inspired premise and fantastic soundtrack, but it's been available free for about five years now, and the Steam version doesn't do enough to warrant a purchase over just playing the free version. It does have achievements and trading cards, both of which are pluses, but the game itself is still just a short novelty, albeit an interesting one. Full 360 controller support is missing, something that really isn't acceptable in a commercial platformer, and while the game has a level editor, it doesn't come packed in with the Steam version for no explicable reason. The only real reason to pick this up is if you played the free version and want to support the developer, which is admittedly why I picked it up when a coupon came my way.
I like eversion's style, it appeals to me a lot, and I loved it when I first played it, but I wish that the Steam release had at least gotten some basic additions like another set of levels to play through, full controller support, and having the level editor included, or even better having Steam Workshop support for custom levels. If you're paying for the game, you're going to be disappointed, and if you're paying to support the dev then why are you reading reviews. I like this one too much to thumbs down it, but the paid version does way too little to warrant any enthusiasm.
Also fair warning it's pretty damn hard, especially if you collect all the gems, though given the short length that's kind of a plus in my book.