If Ghouls and Ghosts and Actraiser had a baby, and they had a twisted uncle called Donkey Kong Country, then that's where Volgarr came from.
A new game done in the style of old, it really is quite a gem. Simplistic as can be in terms of gameplay, though that is not to say that learning how to control Volgarr is not an obstacle with a nice skill ceiling. Some may consider his controls rather rigid, but if you learn how to use him, he's fluid and most importantly, much like Ghouls and Ghosts, very fair. Remember guys, sometimes you have to jump back a bit before you jump forward to get to where you want to go -- little ghouls and ghosts tip for those not used to this jumping system.
From a level design perspective, I personally quite enjoy both paths of the game. However, I think overall the Valkyrie path has superior level design. The crystal path suffers a bit from too many enemies and not enough platforming, but, that may be your thing. Enemies are in and of themselves obstacles, but the game is at it's best when you have to manage both at the same time. So learn to Volgarr well and experience the bliss of the Valkyrie path.
The soundtrack is pretty good, but not good enough to warrant listening to it beyond your 50th hour of playing -- though I think most won't play it that much, so you're fine!
From a replayability perspective, the game doesn't offer much variety once you complete both paths. There are no alternative ways to play, so, once you've beat it, you can either stop there, or grit your teeth and become the best Volgarr player you can be. As a speedgame, Volgarr is simple, but very skillful and both a joy to play and to watch. It may not look particularly "fast", but, trust me, there's always time to save. So if speedrunning is your thing, by all means pick it up and grace the leaderboard -- please, I seriously wish more people ran this game.
From a guy who has too many hours in this game, with only many more to come. (And, I should note, I have the GoG version of this game as well, so... there's more time devoted to this than just what steam wants to tell you.)