I just tested the new movement code and it's great

The stairs ascent & descent is much smoother and, if I'm not mistaking, the gravity change can be accomplished only if there is a ground at reasonable height above the player?

I was thinking about the potion switch idea and, unfortunately, I believe that we should abandon it because there are situations where this system will just not work. Take this situation as a mild example: You need to pick up illusion potion from the ceiling so you use gravity potion to get to the ceiling, but in order for you to come down from the ceiling you need another gravity potion. So the ceiling is completely useless because once you are on the ceiling you can't carry anything else from the ceiling because you need to take gravity potion in order to come down.

We should look into having some sort of spell inventory or similar thing in the game. My favorite concept is the one from Clive Barker's Undying:
http://www.filefront.com/17346826/Undying_SpellInventory.wmv
..we could have right-mouse-button-click-and-hold in order to open spell inventory & mouse-move (while holding) in order to browse through the spell inventory, but I'm not against any other concept.