Rated 4 out of 5 stars

I'd give it a 5 star review but I hate how it put "Web Cache View" in the context menu at the top of it, above open in new tab, which I use often.

Because of this I disabled the addon and enable it only when I need it.

Otherwise, it's a useful tool.

This review is for a previous version of the add-on (1.9m5.1-signed.1-signed). 

fixed in last version. now it is shown after Reload menu item. btw, you can open new tab in background by middle mouse click on link or by Ctrl+LeftClick.

Rated 5 out of 5 stars

This add-on helped me recover some pages from Google's cache, but it also comes in handy when a site is unavailable.

This review is for a previous version of the add-on (1.9m5.1-signed.1-signed). 

Rated 2 out of 5 stars

The cache viewing add-on turned out just a Web Archive shortcut context menu generator.

This review is for a previous version of the add-on (1.9m1.1-signed.1-signed). 

1) All works as expected.
2) Not only Web Archive.

Rated 1 out of 5 stars

stupid questions: HOW DO YOU USE IT?

This review is for a previous version of the add-on (1.9m1.1-signed.1-signed). 

Two ways:
1) Right click on the link and choose "Cache View" to open cache view of the link.
2) Right click on the page and choose "Cache View" to open cache view of currect URL.

Rated 2 out of 5 stars

nice idea actually, but it almost never works. e.g. the addon always sends one "http://" too much to "webarchive", so that you have to correct it manually.

This review is for a previous version of the add-on (1.9m1.1-signed.1-signed). 

Sorry. It is WebArchive site problem. They changed URL syntax. I fixed it now in Web Cache View Plus 1.9m2 version.

Just wait the acception of new version by mozilla or you can try
https://addons.mozilla.org/firefox/downloads/file/183624/web_cache_view_plus-1.9m2-fx.xpi?src=devhub
but this link can not work.