Still remember when we got our first ST520 to try out that was seemingly rushed from their labs (still had hand-soldered cables on the board) - this small machine was revolutionary for that time when we were making the screens of IBM PCs the price of a car glow green in the night. It had most of the things you could wish for, but at a fraction of the price.
What followed where long development nights / weekends first with Basic then digging deep into Motorola's 68000 assembler and C. Not to forget endless hours of playing Hitchhiker's guide to the galaxy (yes that was a text adventure).
With his C64 and the ST520 Jack has strongly contributed to spreading knowledge on computing and providing many a possibility and access to learn, practice and excel in this field of technology. All major computer companies that directly or indirectly are drawing talent and profiting from this till today should thank him greatly.
(For those who have never touched any of those machines - most likely those who you learned from or who thought you courses at University have and learned / discovered many things they are now able to pass on.)
Now that was forward thinking -- brought MIDI sequencing to the masses.
--- [Additional Edit]
The C64 is also getting alot of love today from musicians due to the wonderful soundchip it had.
There is a great company called "MidiBox" that provides kits for you make your own "8bit soundmachines".
One neat thing they were developing, but never came to light, was Jaguar VR. It was a virtual reality headset, using IR-tracking, which let you play VR games. Only a few working prototypes exists:
VR headset: http://www.youtube.com/watch?v=MFZCgNBxkcM
Game shown: http://www.youtube.com/watch?v=GJmnmRzWipo
Another of VR headset: http://www.youtube.com/watch?v=1NCQJrd-4rk