Still a bit buggy. Rated 3 out of 5 stars

This is what I was looking for. But it still has a problem with dictionaries that are very similar. In my case it repeatedly uses the British dictionary when really I need the American one. Maybe there should be a way to set the preferred order in case of there being the same amount of errors in more than one. And another open question is what happens when the right dictionary just lacks some words that a wrong one has included.
Another thing I wonder, is why it seems to only check part of the text, instead of all of it. It seems to depend on the cursor position. Please remove that, or at least let me disable it.

If those things would be fixed, it would be perfect though.

This review is for a previous version of the add-on (0.3.0). 

Thanks for your helpful comments.

Regarding the AE vs. BE problem: I'll think about it — it's somewhat difficult to make everyone happy.
Why is the addon only scanning part of the text? Well, first of all that's a performance consideration. It's just too expensive to spellcheck everything all the time. It would of course be possible to use "cached" spell checking results but I'd rather keep the code simple. Additionally, I write a lot of bilingual text, so I want the addon to change language when I switched languages in writing e.g. an email.
The cursor position things are an experimental addition in 0.3.1 (beta). In 0.3.0 you should not see something like that. Taking the cursor position into account is crucial for writing bilingual text and for people who have predefined email footers. An option to disable it seems sensible though.

I can only dedicate a very small amount of time to developing this addon. If you are a developer, feel free to work on these issues; feel free to contact me with further questions.

0.3.1 is still in the sandbox ! Rated 5 out of 5 stars

switchasitype ver. 0.3.1 released October 18, 2011 and still in the sandbox?
Continuously dealing with French & English, this add-on is pertinent and efficient. Waiting 6 weeks (and more?) for a version to be officially disclosed is a bit long... 0.3.1 works very well, one of the add-ons I call the most.

This review is for a previous version of the add-on (0.3.0).  This user has a previous review of this add-on.

Thanks for the encouraging words. 0.3.1 still has some minor issues that I want to fix before making it a non-beta release. I hope I'll find some time in the next days to do so.

Rated 3 out of 5 stars

It works mostly fine for me, except one tiny problem - I prefer using British English as English dictionary, yet this Add-On keeps switching to American English - Probably because of the similarities, I guess.

Anyway, it would be great if there was a way to prioritise some languages over others, maybe even exclude some entirely (you can't deinstall the US English dictionary, at least I couldn't, so just turning it of for this extension would be good), and/or to "hard-set" a certain language by hand for a while.

Another idea would be an option to set/remember language by site - so I can type German on German sites, English on English sites, and so on...

This review is for a previous version of the add-on (0.2.2). 

Glad you liked the addon. For the next version, I'll think about some way to make British English and American English work at the same time. The language by site option isn't something that I would be using personally. If somebody wants to add it, this is free software, so feel free to contact me and work on it.

Rated 4 out of 5 stars

It works perfectly for me (tested with English and German dictionary installed) and it switches really fast, even though the code looks rather expensive. I see some room for improvements (still not worth 5 stars), but it's pretty good.

This review is for a previous version of the add-on (0.2.2). 

Rated 1 out of 5 stars

I don't see it work either (ubuntu, FF4, default language: Polish, doesn't switch to English at all as I type)

This review is for a previous version of the add-on (0.2.2). 

Could you try the latest version 0.3.0? It fixes some startup issues.

Rated 5 out of 5 stars

Wow. Didn't think it really works that good. Really nice idea.
As I change between three languages it's very useful for me.

This review is for a previous version of the add-on (0.2.2). 

Rated 5 out of 5 stars

Works as advertised! Very useful add-on! The only glitch: on Firefox 4 it doesn't tell you to restart Firefox, but it doesn't work until you do.

This review is for a previous version of the add-on (0.2.2). 

As of version 0.3.0 the addon detects installed dictionaries without a restart of firefox.

Does not work. Rated 1 out of 5 stars

Maybe it is a faut of another extension: After the Deadline. But I tried few times on different websites and it just does not work. Only wants to spell in default language. And, yes, I have two dictionaries installed.

This review is for a previous version of the add-on (0.1). 

In 0.1 there was a problem recognizing all the installed dictionaries. That's probably the reason why it would always jump back to the default language. Feel free to give it another try now.