I may be one of the few here, but I actually like the new system better than the first game's. My playstyle in PoE1 went something like this: Avoid taking companions or training adventurers of the Vancian caster type (Priest, Wizard, and Druid) since their spells are all "per rest." Use as many classes as possible with per encounter abilities or casters like Chanter and Cipher who can freely use all their spells each fight without worrying about using up my precious camping supplies. Only use camping supplies when I find a new set of camping supplies and can't loot them because my current stock is full.
Okay, I did end up using a priest for pretty much every playthrough. So, I only used Radiance and Interdiction in every fight and then only cast a per rest spell when it was absolutely necessary. I felt forced to take the priest with me because without his buffs and debuffs, certain fights became a pain. For all the 90% or more fights that a priest wasn't really needed, and before spell mastery, he felt like dead weight. Once I got spell mastery, I'd use those in every fight too and that made the character feel more useful. Now every caster's spells behave as if they had that spell mastery for each one except they get two casts instead of just one. Guess what? My casters cast every fight now without worrying about camping supplies and I like this.
Right now I feel like every caster has a place in my party because I don't have to worry about camping supplies and resting to restore spell uses. If they had kept the old system for casters, again, I wouldn't be using them except where I felt they were absolutely necessary. I'm really shocked at how good the new system feels right at launch. Can some things be tweaked and improved? Absolutely. I expect that Obsidian will continue to change the game for the better in the future like they did with the first game, but overall, I'm really happy with the game the way it is now.