Useful! Rated 4 out of 5 stars

(Version 0.6.2 - review is updated since 0.6.1.)

I find the app to be increasingly helpful with maintenance done by the author. Thank you for the useful extension!

It saves me time in entering math symbols when I'm typing math answers (usually on Yahoo Answers).

easyMath has a good selection of math symbols. Additional Greek letters can be added in the Preferences from the Firefox Addons page. It is still missing some very useful math symbols however. It can not possibly have all of them because in many cases the Unicode character isn't going to be in the fonts that people have installed, and there's not a really easy way to point everybody at a good font that they can download, that I know of.

Some characters that I've needed to obtain from other sources because they're absent from easyMath:
Angle: ∠
Set theory: ∪ ⊂ ⊆ ∅ ∈ ∉
Number theory: ∤

Ideally I could get to anything on this page without having to open a different window or go to a new page:
tlt.its.psu.edu/suggestions/international/bylanguage/mathchart.html

The symbols appear readily in a sidebar right next to the page. I just type control-alt-M to make it appear, and click an x in its corner to make it go away.

I find the appearance of the panel to be somewhat poor, as there are bright red areas and words that half overlap them, but the characters are easy enough to find on the page after a little practice.

It appears to me that the add-on has been checked for security by the Firefox add-ons team, according to this FAQ:
https://addons.mozilla.org/en-US/faq : "Are add-ons safe to install?"

"Unless clearly marked otherwise, add-ons available from this gallery have been checked and approved by Mozilla's team of editors and are safe to install. .....

Learn more about our approval process:
https://addons.mozilla.org/en-US/developers/docs/policies/reviews"

Some forum activity seems to indicate the Yahoo team has been lax about this, and oblivious to feedback, in some cases. So some kind of blind trust may be needed, or some credentials about the author, or else I need to see the source code (is it there in my computer where I can find it somehow? ....)

A suggestion: if I click the button for a character, it is sometimes useful if it would be copied into the clipboard so that I could repeat it without re-selecting it. I think that shouldn't be the default though. A shortcut to repeat the same letter as selected would be useful.

This review is for a previous version of the add-on (0.6.1). 

Thanks for your review

It seems that I have fixed the problem with jumpy scroll, correct me if I'm wrong.

Also about additional Greek letters. I might haven't made it clear enough in the add-on's description, but you can configure which Greek letters to show in Options window (which you can open from Add-ons list).

I would like to add additional symbols (as your suggested angle symbol), but there is problem I don't really know how to deal with. The "∠" is from Cambria Math font. It is one of the most complete fonts regarding math symbols, but it's not a web safe font. Creating my add-on I have chosen Times New Roman font and included almost every character I found usable in maths. I still don't know if I should include characters from other fonts.