Welcome to the board Imiss.
As far as the hesitation goes, personally I don't think you even have to wait 'till 300 miles -- I think it's there right from mile 0. It takes most people a few hundred miles though to "get the feel" of the car before they can state whether it hesitates/sutters or not I guess.
I'm glad to see you're not going to get the car until the issue is resolved - personally I love the car but at the same time I refuse to recommend it to a single person until Mazda fixes it....and if they don't, 0 recommendations will be coming from me.
But like I said, I still love the car and I kind of think many people could solve the problem (or at least greatly reduce the problem) with some of Joe's great fixes - (especially the FPR). For now I'm going to try to wait it out though and see if Mazda comes through with a fix. If not, then I guess it's Joe's FPR for me.
1 thing I sure wish I could do is drive the cars of those that say they've never had the hesitation problem (Yashooa is one that comes to mind). It's just impossible for me to believe that they've never had it when the car was stock.......................we're all using the same ECU after all.