I have a love hate relationship with class levels. On the upside you can create a non-player character fast and eyeball encounters pretty easily. Point based characters can be customized more, no contest there. On the other hand I'm using a rules light system. Four stats, five skills and more customizing means more rules.
Microlite20 gives every character +1d6 per level, +1 to attack rolls and +1 to all skills. That's a little too streamlined for me. Why should mages advance in all attack rolls the same as fighters? It makes the fighter bonus to attacks and damage much less important (+1 at 5th, 10th etc.)
I'm tweaking leveling up as follows:
HP STR +1d6 per level.
Skills +4 skill points per level. Max of Level +3 skill points in any one skill.
Heroic Points + 1d6
Attack Bonuses for physical and magical combat are as follows:
Fighters, Monks 1/1 level (1/2/3/4/5/6/7/8/9/10 etc)
Paladdins, Rangers, Clerics 2/3 levels (1/1/2/2/2/3/3/3/4/4)
Rogues, Bards, Druids 1/2 levels (1/1/2/2/3/3/4/4/5)
Magi, Illusionists 1/3 levels (0/0/1/1/1/2/2/2/3/3)
Magical (includes thrown spells, and level bonus to Will checks)
Magi, Illusionists 1/1 level (1/2/3/4/5/6/7/8/9/10 etc)
Paladdins, Rangers, Clerics, Druids 2/3 levels (1/1/2/2/2/3/3/3/4/4)
Rogues, Bards, 1/2 levels (1/1/2/2/3/3/4/4/5)
Fighters, Monks 1/3 levels (0/0/1/1/1/2/2/2/3/3)
That's not too much extra work. It also gives me a framework for making saves. For example a mage might get +1/level to modify a save against magical charms. He'd only get a +1/3 levels to make a Will save to resist pain though (that burly fighter would get a +1/level though as he's been cut up many times and kept fighting.)