I find it hard to believe that power supply problems would cause a modern, high quality but minimal frills keyboard to malfunction in the ways I've seen.
My initial setup was with the keyboard and mouse connected to the "console" ports on my DVI KVM switch. This means that they are shared with several other computers, all of which have no trouble with them. The KVM switch is itself a powered hub as far as USB is concerned.
But even with the KVM switch connected via my Belkin powered hub (which itself is powering the R-Pi), or with the keyboard and mouse connected directly to said hub, the keyboard was consistently locking up occasionally at the console, and barely functioning at all in X11. Yet at any time I could switch to a Windows PC or my PowerMac G5, and they would have no trouble with this same hardware, still connected to the KVM.
Eventually I disconnected the desktop keyboard and mouse, and instead plugged in a wireless transceiver for a miniature keyboard, meant for HTPC use. Now the keyboard and mouse are reliable, albeit with the usual quirks this particular keyboard brings with it.
I only have a few USB keyboards. I should probably try the others when I get a chance.
The key to knowledge is not to rely on people to teach you it.