I like the gestalt rules, but I would only implement them for certain limited kinds of campaigns. Nifft's ideas are nifty. I could also see using them in a campaign in which I wanted to do Ars Magica style troupe play. Each prime PC (the equivalent of an Ars wizard) would be a gestalt. The companion level PCs would be regular D&D guys and the grogs would be NPC classes. My friend Pat likes the idea of screwing with the powercurve of D&D by forcing PCs to use the NPC classes for their first X levels, then allowing PCs classes for Y levels, then finishing off with Gestalt levels.