Interesting.......Some people are better with numbers so a numerical system works.
Some people think by sounds so a do re mi works better.

I saw a documentary about a fantastic pianist who was autistic. He could play anything note perfect after hearing it just once. He could jam with great jazz bands and play music in any style from classical to jazz. He could not tie his shoe laces or write his name...the strange thing was he heard colours. Each note had a colour and he just played the colours.

I once saw a keyboard that had all the notes labelled similar to Mark's pic to help people play and understand. It had do re mi and a b c etc but it also had colours.....belive it or not the colours worked as they stood out and were easier to work out.

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055