I have never used rotella, but started hearing about it more when I owned my WRX for a year. I used to be a Royal Purple or Mobile 1 kind of guy as it is readily available. I took GT5.0FACE's advice on the MTG for the M6 in my mustang and was heavily impressed as far as performance goes. It really did make a massive difference. I used amsoil stuff with the next oil change and felt like the motor sounded quieter (subjective). I read up about their oil filters being pretty damn good, so I just assume to spend more money up front for better protection down the road. I was wanting a oil-less air filter that would fit my Roush intake and amsoil actually makes one. Seems like you have to pay more for their products, but it is good shit from what I can see.
I was wondering how many people ran it, or just opted for a different product that wouldn't cost as much. They have a membership that allows you to get decent discounts, but being a dealer allows some other perks I am sure. I know some people like to change their oil every 3k miles, which spending money for amsoil wouldn't make sense for that though.