I've been running my first 4 stroke for about 3 months now... Magnum .91. From my personal experience, it is no more difficult to operate than any of the two strokes I have. In fact, I've had LESS trouble tuning the Magnum than I have had with my 2 strokes. Once it's set, that's pretty much the end of it. The only thing you need to pay closer attention to is the break in proceedure. I dont know about the others, but Magnum outlines this step by step in their manual. I run the same fuel in mine as I do in my 2 stokes (17% nitro, 18% oil). It will need an occasional valve adjustment, but that's easy to do. I would say if you want a 4 stroke, go for it. You wont have any trouble if you just follow the break in recommendations and feed it good fuel with a minimum of 18% oil.

Oh yes, as Ken said, get yourself a tach... it makes tuning much easier than by ear until you get the hang of the different sound. And what a sweet sound it is!