So how many use MM cartridge and intend to keep it that way ?

Hmmm...

I have never had a turntable with anything other than an MM cartridge so I have to ask, is there THAT much of a difference?

Me neither.. curious now. Damn it.

IMO, Every single cartridge brand and type, regardless of how it works (MM, MI, MC), sounds at least a little bit different from any other cartridge.  Whether that difference is worth worrying about is subjective.  Among the different types, I have found, thanks to Raul et al, that I prefer MM and MI over all but a very few MCs.  ZYX UNI is one of those MCs I like a lot.  Funnily because it displays some of the best qualities of MM/MI.

Inna, Makes sense to me to have four turntables, actually.  But I am nuts.

Albert has two tables and four arms, all MC cartridges, though. Makes sense to me too but probably would be too much for me. Two cartridges ready to play at any moment would be enough for me, I am quite certain.

Hell, I'm happy with one. What's wrong with me?!