I've started doing this. Bought a large panel fixture and a separate high-quality LED current source and it has been absolutely great. Next time I build a house I'll probably run all the lighting circuits on a hefty 24VDC main power supply with small DC/DC regulators on every fixture. There's no reason nowadays why lighting circuits should be 120 or 240VAC.
Like I said in a previous comment, with LEDs, power requirements are small and distances within a house are small. Coupled with a resonably high but safe voltage (like 24 or 36VDC), there's no reason why 14 gauge copper wire couldn't work just fine for a lighting circuit.
