A couple of suggestions:
1) Make "English (US) utf8" the default
Comment: Why not make it the default? Any reason? I mean, almost everybody is using UTF-8 as the default, and it shouldn't corrupt sites previously in ISO-8859-x switching to UTF-8. Anything I'm not aware of? Size footprint is too small to make any difference (and non-existent if the site is using characters within the ASCII range only).
2) If it won't become the default, change the priority of "English (US) utf8" to 2 instead of 9. This way it is right after the "English (US) latin1" language.
Comment: So us who need to use UTF-8 can easily see "English (US) utf8"
3) Change all lang charset in the regional tab to uppercase - which is the preferred format of the body in-charge of it (which I can't remember right now).
Comment: Lowercase is fine, no problems with that, but I think since these locales comes packaged with b2evo, and in a sense default, then maybe b2evo should opt for the preferred method ;)
4) By default (installation and upgrade), the only "active" (ie being shown) in the Regionals tab are "English (US) utf8" [and "English (US) latin1"].
Comment: There seems to be a problem with setting/editing the priorities when there are too many languages "active" (enabled or not disabled).
If I edit a language to Priority 2 and there's another language that's Priority 2, everything goes into a mess. I have to click each language to "reset to default" even though I don't need those languages.
Btw, I upgraded from 3.3.0-rc1 to 3.3.1-dev and new languages were installed - which I don't really need. To a normal user (and those who are using fantastico and similar) they'll upload everything. But to an advanced user, yes, it is easy to delete.
Hmm.. I guess those are my suggestions ^_^
Last time I check there were still an awful lot of hosts not properly supporting UTF-8, especially in the US. I made a note to recheck.