i have 5 installs and i wish i had made 6, but seeing as im only two boxing nowadays it doesnt really matter anymore. the reason being when i play my main solo i use max resolution and all the jazz, but when i do into dual box mode my resolution is altered and it moves all of my action bars and other things like unit frames shift a bit. so i then have to adjust that stuff to dual box then when i fire back up for single boxing i gotta adjust it again.

but i dont do it often anymore so no biggie really and i really could just reconfigure keyclone and one of my other installs to handle it i just havent. but that to me illustrates another possible pro of multiple installs.