I think having looked over it, here are areas of concern:
Wizards get the 3rd at-will. They have a lot of good choices and sometimes having that 3rd choice would be really great.
Hybrids. This would be really awesome for them. When a class has two great at-wills, but it can't make it happen.
Immediate-heavy builds get a 3rd choice. Swordmage, Str/Dex Rangers, etc...assume that from an optimized perspective, most builds would want a 2 encounter nova+2 immediate actions. After round 1, they're using at-wills - so this represents a power up to some optimized builds.
Psionics. This should only be an at-will, not augmentable.
I'd probably also give Half-Elves both Dilettante & whatever the new ability is. They still need to spend a feat to make it at-will, but this way works similar to Humans.