Again it has been very handy having a multiple monitor setup at home. I can have plenty of space to run WebStorm, NotePad++ etc. on main monitor and Chrome on the second screen where I can test the running application. My second monitor was a free, not super high resolution but still darn handy. Get one if you don't already have one, they are a programming life saver.
Currently I have the following working on the canvas:
Paint time margin (with various gradients)
Paint column headers
Paint grid lines
Paint dead areas outside of grid
Hold down middle mouse button and scroll around in grid
Various "objects" are set up, same objects as in the other implementations. I learned how to get the canvas to resize to fill the screen as you resize the browser. Mouse interactions including up, down, move and exit are in place. I am sure I am still doing various things incorrectly or the hard way but the code appears to be pretty clean and the paint codes runs nice and fast.
I don't see any painting limitations and the canvas 2D API is feature rich and very fast at painting. I need to chuck the code over on my server and see how it runs on the tablet when I get a little farther along. I also need to tie in the touch events to match the mouse events which should be very easy to do.
Where is will get interesting is in all the user interactions. On the PC you have click, double click, left / right / middle button processing potentials. On a touch device you have tap, double tap and long press. There are times you have to get really creative to handle user interactions. Normally on a touch device a long press will bring up a menu and double tap does a default action (which should also appear in the menu). On a PC a right click shows the menu and double left click is default action.