Echodork, if my memory serves me correctly, Nintendo didn't scrap the idea to remain cartridge-based. Sony had a deal with Nintendo then decided to make their own system (The PSX) and in doing so basically became Nintendo's competition.
this sort of betrayal (since Sony was to provide nintendo with the CD-roms etc for the new system) made Nintendo a little irritated and that kept them on the cartridge route. I believe if Sony hadn't decided to make the PSX and just continue with Nintendo then Nintendo would have gone CD long ago.
btw, mario paint mouse rocked
For at least the one game it was for. As far as the expansion on N64 and the memory cards. They were used quite a bit. The memory cards were mainly for extra saves on games, where the cartridge space wasn't enough. Granted, the Virtual Boy was a failure, and I really disliked the super scope as well.