I've mainly played my mage for about an hour and a half so far today. Nothing new to report about the quests, since I went through them all on the cleric on days 1 and 2. Things obviously go faster having been through them before, and my mage just hit level 8 before a lag spike followed by a familiar notice: "This server will be shut down in 60 seconds. Please log off."
I'm impressed with the mage so far. It's enjoyable being a "clothie" and still capable of soloing. My mage has enough firepower, combined with movement-impairing effects, that he is able to single-handedly take on mobs one or even two levels higher than him. Pretty good since I wouldn't have taken on that challenge with my priest at level 8.
The mage has a damage shield that has a 1 minute cooldown and lasts for 4 minutes. It's fairly mana expensive, but it's great for when the higher level mobs make it to within melee range. One drawback to having a mage is there is basically no melee capability, so don't even think about going toe-to-toe with ...well, anything. However, the pushback that casters sometimes experience in MMORPGs is not present in Aion, therefore you can safely cast on a mob that is beating on you without an increased casting time. Kind of nice, but I still wouldn't plan on being able to absorb much abuse. Hopefully you just have another second left in your final cast before the target is dead. Otherwise, you'll probably be the one dying.
My plan for this mage is to specialize as a spiritmaster so I can try out the pets. I've seen them wandering around and they look pretty interesting. Hopefully I'll be level 10 tomorrow and be able to get into that aspect of this caster.