I like Potion games.
I love cards where Potion is more than just extra opportunity cost, but rather an interesting twist in how the card works, as seen in Alchemist, Vineyard, and Apothecary, to some extent.
Some cards work well even just using Potion as an extra access barrier, like Possession, Scrying Pool, and University.
For some others I think the coin price is too steep, resulting in unsure results after your big Potion investment. I think I would prefer Familiar at 2P and Golem at 3P. Alchemist at 2P would probably make Dominion a slightly happier place too.
Philosopher stone just doesn't work too well with a Potion cost.
Transmute just doesn't work too well, but man, I wish it did.
I'd love a few more Potion cards. I think Alchemy suffered from having a few unpolished cards (and a few slow cards), rather than due to Potions alone.