Small update:
AFAIK
that only leaves the current version (4.85.1.386, released August 8 2010) as being identified as "as a variant of Win32/MessengerPlus potentially unwanted application", while all other scanners don't see any problem with it. I don't see why Eset would still have a problem with Plus!. CiD isn't there. They already unblocked download.msgpluslive.net. And nobody, including anti-adware apps, seems to have a problem with the current Conduit/Ask.com sponsor packages. Perhaps they forgot about Win32/MessengerPlus when they were removing the download.msgpluslive.net block.
Oh, and certain older Plus! versions are still identified as win32/adware.cidhelp, but nobody should have a reason to use those anyway, so that should be ok.
EDIT: Actually, it seems MalwareBytes was a bit lazy in lifting the ban. Let's hope they completely lift it soon.
EDIT2: MalwareBytes stopped flagging Messenger Plus! (and the site)
completely.