You are the first one to report such issue. Can you provide more information ? Maybe you have the view gridlines enabled. It is a firefox regression which causes canvas to be slow when those gridlines are enabled.
Very nice add-on, but a bit bulky in appearance. A smaller magnified area box with thinner boarders would be nice. Perhaps an interface that looks like a magnifying glass that turns the magnification up or down by scrolling the mouse wheel. Also more precise control over the level or power of magnification. (e.g. 1 to1.1, 1 to 1.25, 1 to 1.5, 1 to 1.75, 1 to 2.0 and so on) Then at 2x it could increase in whole numbers. Currently even at the lowest magnification it tends to give a boxed in feel only able to read a single word or part of a word at a time. Needs some tweaks, but it's still a nice and much needed add-on in Firefox.
I do understand. i meant to give 4 stars the first time around, but ended up with three. My apologies. A simple accidental mouse click and I hadn't even noticed until you pointed out I gave it only 3. I edited my review and set it to 4 stars.Of course as you can surely understand with the add-on in it's current state I can't in good conscience give it 5 stars. 5 stars and a 'stellar' review will come when the changes discussed are implemented. I look forward to the upcoming changes and then spreading knowledge of this add-on's existence. Even without the changes thank you for your efforts in making an add-on of any kind.