I like it. It makes it a lot easier to hand out XP for treasure and events by reducing the numbers to a consistent 100; at the moment I'd first need to look up the EXP needed to level table, and try to decide what percentage of that I wanted to give out, whereas this streamlines that process.
I'd probably tinker with it a little. I like the idea of giving out EXP only for Hard and Deadly encounters, rather than dicking about with every individual monster. Having a magic item give you part of a level is also quite pleasing, and something that fits easily into a hero's journey narrative.
Overall, while I'm not certain that I'd jump ship to this immediately, I like it a lot more than the default EXP system. The real question is whether I like it enough to use it instead of Milestones.