Hold on a second, this is meant to be an incredibly simple computer device. I really REALLY like your ideas though. I've been planning an SP-15 computer which would use the same or similar instruction set, have an LCD screen, and have multiple program slots, each 256 bytes each. This SP-15 computer will come after the SP-10 is finished though.

This might turn out to be a whole computer line I sell and market for student and hobbyist use.

I've updated the table http://withg.org/spyro543/sp10/index.htm
And there's a Youtube video now!

Man, you should totally get some of these switches:
http://www.ebay.com/itm/5-X-Green-Momentary-On-Off-Push-Button-Micro-Switch-NEW-/350764915239?pt=LH_DefaultDomain_0&hash=item51ab37da27
http://www.ebay.com/itm/2-Pcs-Toggle-Switch-DPDT-on-on-2-position-super-mini-3A125VAC-blue-New-STDD-/281090792532?pt=US_Home_Audio_Amplifiers_Preamps&hash=item4172511c54

No, when shifting, the 'new' bits are filled with '0' (or '1' if it's signed and right shift)
When rotating, the bit that leaves the byte/word etc is added to the end, so when shifting right, bit 0 (LSB) becomes MSB.

So there's quite a difference in usage too

Very interesting project. If you'd be willing to connect one of the LED outputs to a line-out, I might try to write a simple sound output routine at some point.