I don't think anybody would, or could, argue that the SuperPET was a mainstream computer. It was developed for an in conjunction with the educational market and sold fairly well. Here in Ontario it was available in retail stores albeit those that focused on computers rather than retailers like K-Mart and Canadian Tire who stuck to popular home computers like the VIC-20 and 64.
I think the appeal of the SuperPET is its flexibility in terms of programming languages and with a Super MMU board (see my earlier photo) you could run OS-9 which is a giant bag of nerd fun. There actually is a fair bit of software for the SuperPET although it isn't as widely distributed as software for the more mainstream machines. While my VIC-20 and 64 were arguably more fun, I *loved* my SuperPET. Speaking of which, I hate to miss an opportunity to post this picture so...
Anyway, this is Denial VIC-20 so it's probably in poor taste to describe anything other than the VIC-20 as being the "greatest computer of all time".
P.S. If anyone is looking for a SuperPET in mint condition, in the box no less, with or without a Super MMU board, send me a PM and we'll talk.
In the end it will be as if nothing ever happened.