So when frogboy first tossed the idea for spell levels, I was all excited. What i thought was going to happen was that each spell had a level and you could continue to hone that specific spell.

For example:

Lightning bolt: Level 1

Mana: 20

Damage: 1 - 15

Range: 6

Lightning Bolt: Level 2

Mana: 20

Damage: 1 - 18

Range: 6.

I believe a system where we can continue to improve spells would be very nice. It could be as simple as reducing the mana cost of each spell by a fixed percent or as complicated as the following:

Congratulations, you have leveled up "Lightning Bolt"

You have 3 points to spend

Range: +0.5, increase per point spent (truncated).

Damage: +5% per point spent.

Mana Cost: -2% per point spent (mana would increase as the other attributes increased for balance purposes. This would reduce that inflation).

Anyway, this just some thoughts.