Except that the beta is far from terrible for many. And that the GM is usually well ahead of the last betas that it can be different enough. Facts about something that doesn't even exist yet (at least in the capacity of anyone being able say anything about it) simply can't be facts, and that's the only thing that would actually be an actual fact in all of that.
The beta should be consistently fast on all devices (with a clean install).
You don't have any facts that its "far from terrible for many". I have just as many facts about it being terrible as you have for it not being so.
Every single video I have seen of it on the 4S shows it being slower than iOS 8, which it shouldn't be. Why? Because Apple supposedly put a lot of time into optimising their code, and in addition to that, it should not be any slower as there are no new features that would be any more power consuming on the 4S.
iOS 8 was the same. The last beta wasn't great, and neither was the GM.