Quote: "I may have spoken too soon."
As usual, the problem is with expectation as much as with performance. FPSC can be used and worked to make a decent game with a playable frame rate, but it takes some time, practice, and learning about the strengths and weaknesses of the engine.
A very simple drag-and-drop engine will make a very simple game. If you want more, you'll have to push the engine and learn how to make it perform. It's not easy, but it can, and has been done.
It's almost impossible to not have those dollar signs in your eyes when you read the advertising for FPSC. Even though we know that what we're thinking about, as opposed to what we're actually reading, is too good to be true. I can assure you that all of the claims made are true, and the engine will do everything you've read. How well it does those things is up to you.
With that in mind, we know that it's not the engine of choice for the game developers of today, which explains it's price tag. What you've got is a great learning tool, a lot of hours of enjoyment/frustration (whichever gets you off) and a chance to make a viable game title with a lot of time and hard work.
Best.
I'm sorry, my answers are limited. You must ask the right question.