The problem with Spheres of Power/Might is that they've essentially ruined most other systems for me - or at least systems that are "d20 based combat engine with some exploration and social stuff on the side" simulators. It feels like in a lot of systems there's a tradeoff between crunch vs. concept freedom when it comes to character creation, and Spheres successfully transcends that dichotomy. You can you realize essentially any character concept from the get go while having a lot of crunch to back it up, instead of just writing "ice powers" on your character sheet and then playing Calvinball from there.