Some other graphic softwares have the great function - precise zoom by keypad + mouse. In Blender it is Ctrl+Middle Mouse Button and in TVPaint Animation it is Alt+Right Mouse Button. In the second program this function goes more comfortably: mouse or stylus move horizontally. Ones you tasted this option you will miss it in the other graphic software.
This option is much more powerful than to rub the touch strip on wacom.
Please get a look to the example of the power of this feature in TVPain Animation package. There is no any powerful accessebility like this at all. http://narod.ru/disk/55222613001.d5f05b6d28ecf82477605ca3786f58e9/capture-1.avi.html
and the same is here http://www.sendspace.com/file/2ugr6x
And another one in Youtube http://youtu.be/7GmA3OTObQU
Wow! I have just found it! Ctrl + Middle Mouse Button! Let the mouse pointer be the zooming center, remove the lags and it will be terrific! I will not sleep tonight.
Ctrl+Space+Mouse Click zoom at the cursor position now, in a continuous and smooth way as you describe :)
What we really need is a good tutorial on the canvas interaction methods and shortcuts we have :-)