Nimbus is an almost perfeect game. The sense of momentum and the feeling of zipping through the air is really fun. Shooting out of cannons, bouncing off of launch pads, diving from great heighs; it all feels good. The game introduces new mechanics, level features and techniques steadily throughout the game, so it's never stale. The music is great, and suits the relaxing and exhilarating aspects of the game very well. Collecting the coins and completing the scrapyard stages after finishing the main game is also very rewarding and satisfying. The graphics/art style are also superb.
Only problem I had with the game was that the boss battle felt a bit out of place, turning the game from acrobatic/racing game into bullet hell for the last level.