Turn on the V-Sync in your game, please! Otherwise, it's trying to output unlimited FPS and just burns your hardware.
And, honestly, if you decided to go to full 3D, at least make the graphics worth it - like, good quality shadows, global illumination (at least pre-rendered) would help a lot, not just a cheap SSAO.
Will add settings for vsync and frame limit in the next version. Was actually assuming it would limit at by default but didn't actually verify.
The switch to 3D is primarily for the freedom in customization and dynamic interactions which is going to make pre-baked stuff a bit difficult.I do get your point to a certain extent and I'm working on improving the quality through each version, it's a work-in-progress but is going to be more time intensive.