I have. Reaper's routing interface is pretty much a rip-off of Pro-Tools, except the Pro-Tools interface has been placed in a stupid location, and isn't quite as flexible.

I think you're caring about theoretical gains in audio quality that probably don't exist as a practical matter. Unless your source material is all uber-pristine and every component in your audio chain has an insanely low noise floor, it's all pointless. Now, if you're sporting a bunch of Apogee I/O, some Genelec monitors, and an acoustically treated studio space, then yeah, maybe that 64-bit action is actually doing you some good.