Yeah, they're in the same Rapid Release program (for recovering procrastinators). But does Tb10 offer any actual new and useful features compared to, say, Tb9? I was using Tb5; now I'm using Tb9. I'm more interested in stability than keeping up with the Mozillas. It's possible I might not "upgrade" to a newer Thunderbird until the Thunderbutton or some other major new feature is implemented. Being great at sending and receiving messages is enough for me, regardless of the version. Yeah, I'll download it and look at it--just as with Firefox [though with less expectation of useful change, which is pretty low anyway given the nature of Rapid Release].
Thanks, BTW.