A couple of things from last night's playtest:
1. Problem: magic missile works fine at low levels, but it begins to become a bit overpowered at high levels. Getting to score "free" damage every round is fine when it is only 1-5 hit points we are talking about...but when that caster reaches 9th level, it seems a bit much. Sure, he is still not doing as much damage as the fighter can, but he doesn't have to make attack rolls...he is guaranteed 5-25 points of damage every round...more, if the spell has been buffed with Metamagic feats. That's like having a +1 guisarme that always hits and always scores a crit.
Resolution: magic missile should probably require a ranged touch attack roll. All missiles produced by the spell use the same attack roll, regardless of the number of targets.
2. Problem: Metamagic feats are waaaay broken! One of my players, the guy who drives the wizard, is an excellent playtester. He decided that his character would spend his entire life mastering a single spell (magic missile, of course), and has stacked every possible MM feat that he could onto it. By the time he hit 10th level, he was throwing Quickened, Empowered, Maximized magic missiles all over the damn place every single round. He was dealing 70 points of damage per round, every round, without so much as an attack roll (1d4+1 maximized = 5, empowered =7, five bolts = 35, cast twice each round = 70).
Resolution: I have no idea. My first thought was to fix magic missile with an attack roll and call it good, but there will always be another spell to exploit. As I have written them in my draft, the spell level does not increase when a metamagic feat is applied...an oversight that allowed my player to really stick it to me. So I'll put verbage in that will fix that (an increased spell level means a higher caster level DC and higher requirements), but I am concerned that it might not be enough. Anyone got any food for thought?
3. Problem: Lack of healing spells. I don't know if it is a problem or not, but it is definitely an issue that I didn't think would ever come up in a system with at-will spells. Since spells with the (Healing) descriptor only work once per day on the same creature, the "tank" characters end up getting screwed after the first battle.
Resolution: No idea. I don't really see the problem here, but our cleric is really adamant about this needing to be fixed. I just don't know how to do it without creating some arbitrary "x times per day" rule.
This really isn't a problem with the system, per se...just a bit of a departure from the way the cleric is accustomed to functioning. The obvious way to handle a lack of healing magic is to handle it in the game: encourage the players to buy more potions, wands, and scrolls of healing, and I could always sprinkle a few of these health boosters in my treasure hoards.
Anyway. Feedback is always appreciated; I will update and repost the .PDF as I get the time...probably in another couple of weeks.