Rated 5 out of 5 stars
Everytime it starts on Thunderbird, I am asked to submit various passwords (my Mac password, my Gmail password and so on). Apparently it doesn't remember them. I got so fed up that, to be honest, I am not sure whether it actually works after vaulting the internal hurdles. If it worked like it does on FX, it would be five stars for me; but, at the moment, on TB, it's pretty useless. Just a question: why the completely different functionality on the two Mozilla platforms?
Update: Thank you for your quick reply. I followed your suggestion, but it unfortunately didn't work (incidentally, upon start-up, OS X gives me the choice to "allow" or "deny". There is no option to "always allow". I will contact you directly by e-mail to see if we can resolve this. Thanks again for responding so quickly.
FURTHER UPDATE: I followed up and found that the problem was apparently caused by the Google Contacts add-on. Once I disabled that, Keychain Services Integration started working as stated on Thunderbird. Now integrates perfectly in both TB and FX. The dev is always right ;-) and this is a great add-on.
If you've asked OS X to "always allow" access to those passwords and it's still prompting, the usual cause is that your Thunderbird binary has been changed somehow and OS X no longer believes it is correctly signed. Try dragging Thunderbird to the trash, downloading again, and reinstalling.
There's no difference at all in the add-on for TB, Firefox, or any other Mozilla application. The extension implements a standard interface specified by Mozilla and tries as well as it can to map the requests into the Keychain subsystem; the different Mozilla applications may use the interface differently, of course, but in my experience there's not much difference. I don't use Thunderbird myself, so it's not as thoroughly tested there, but many other people use it successfully.