Balance is ok- For the first half it was a bit too fast and most of the bottlenecks are in drawing. Then at the end you spend some time waiting for gold which is a bit odd.
Uniqueness, Fun- I really like that you can draw your own symbols. Some of the common ones get repetitive after a while though. (Drawing unrelated symbols and seeing them spin, however, will always be funny)
Theme- It does fit the theme fairly well- It is alchemy after all. I do feel like just having the symbols be drawn is a little underwhelming, though it does add to uniqueness. Incremental element could be improved though.