I switched from the regular "Thunderbird 2.0.0.6" to "Thunderbird Portable 2.0.0.6" a few months ago, then I received an upgrade notice to 2.0.0.9. I first thought it would be for "Thunderbird Portable 2.0.0.6," so I clicked [YES] to upgrade, then I happened to think it might have meant for the regular "Thunderbird." I went trhough the forum to try to find out whether the 2.0.0.9 upgrade would be compatible with "Thunderbird Portable 2.0.0.6," and sure enough I found some members were experiencing problems with add-ons. In other words, the "2.0.0.9 upgrade" is not fully compatible with "Thunderbird Portable."
So I think it would be better if the engineering team considers differentiating the regular "Thunderbird" users from the "Portable" users when sending an upgrade notice. In other words, if an upgrage is intended strictly for the regular "Thunderbird," please do not send the notice to "Portable" users. On the other hand, if the upgrade is intended for the "Thunderbird Portable," please do not send the notice to the regular "Thunderbird" users.