How do you feel about the magic system? I'm kind of annoyed that you can't just stack charges of a spell in a single flask. Because it's a lot of tedious clicks to make a spell (with whatever potency), get just three charges, equip it, wait until it is used up, make another three charges, equip, etc.
It seems that you get more flasks as the game goes on (I think I have three so far), but it looks like the only way to increase charges per flask is with a catalyst. I.e., there is no simple 'consolidate flasks' mechanism.
So far I haven't used magic much at all; I've only made a few and put them on Ignis or Prompto. Ideally I would want to delegate one of them (Ignis I guess; I think he becomes stronger at magic) to be a primary spell caster, but you can't seem to influence their AI, and I don't like the idea of continually checking my inventory screen to see if the store is used up or not. I suppose the practical way is to include spells in Nacht's play, and equip them on Ignis (or whomever) for battles for which they may be needed.
On a different note, I got to the point where you get the weapons that take HP when you use them. At first they seemed not helpful, but then I realized that since Warping to high points recovers your HP, and you can usually get very far from an enemy for a strong Warp Strike, you can make big attacks with little downside. So Warp, select strong weapon, go for big Warp Attack, Warp again, regain HP if needed, Warp Attack, etc. Switch to your basic weapon if you need to do a lot of regular melee. The attacks with the strong weapon can do a lot of damage. It's a pretty neat play style, and it makes the ability to switch weapons (well, from a set of four) actually useful.