I looks to be an interesting chip, but I'd rather stick with Teensy 2.0 and Teensy++ 2.0 for most keyboard stuff. It's nice to have the choice between those two, with hardly any code/peripherals compatibility to worry about.
My converter keeps macros in EEPROM (where they use 2 bytes per step and a few bytes per macro), and builds an index to them in RAM. Each index entry is 5 bytes. Also, if there are any macros that trigger on key release it has to track key state, which uses another 256 bytes of RAM (once). Layers are expanded from EEPROM (where they use two bytes per remapped key) to a 256 bytes table in RAM per layer.
It doesn't take many 256 byte tables to fill the Teensy 2.0's RAM! Don't forget that a certain amount is already used for variables, stack etc., and in my converter also the base layer remap table and key state tracking etc. Overall there's less than 1K left for config stuff, but that's still enough for most people. And if not, there's the Teensy++ 2.0, which should cope with anything this side of a space cadet
One aspect of the new chip that might be useful for some projects is improved interrupt response time. That could open up new applications. Porting V-USB (software USB) to it would be nice, since it is capable of being a USB host on its hardware USB interface. When overclocked to 96MHz, it might even be able to do full-speed USB in software, just!
Anyway, if the price is right, overkill is irrelevant
