have rode these wheels now for about 6 weeks and they have some small chunks out of them. they are so small i cant hear them or feel them yet though, but i imagine once i hit 12-16 weeks it will be more noticble. i have heard spitfire flatspot easily but i have put these through a lot of fs slappys and nothing remotely close to a flat spot. i think that might be contributing to the chunks i have, proably just powerslid into some sharp rocks on the way on to a fs slap. so could be more the way im skating and not so much the wheels too cause i just learnd this trick few weeks ago.
The original formula definitely had more flatspot issues, but the Formula Four wheels have way fewer problems overall and although I have seen a few sets over the years with flatspots or problems, they are all what I would consider "user error" or not defective, eg nail sticking out of a box took a chunk out of a wheel, board ran under a car and got major flatspots from being dragged, power slides to a dead stop that caused small flatspots, etc.
I guess everything in skateboarding is going to get used, abused, worn and destroyed, but it sure is nice to have things like wheels that tend not to flatspot as much as others.
That is why my pick is Formula Four wheels, but everyone is entitled to make up their own minds too.
More often than not when I hear some older guys or people who have been skating for a while talk about "Shitfire wheels" and saying Spitfires suck, it is more often than not because they had the original formula and not the Formula Four wheels, but sometimes that one set they didn't like will give them an opinion on things for the rest of their life. Again, not a big deal, but it is funny to hear some people go on about things, when I feel like they know little to nothing about them in the current day and age.
What size and shape are you currently riding?