IME, playing a pixie is very fun, but not very optimized.
The real limitation is that pixies will always have jack squat for hitpoints. They do well as a skirmish style class (rogue, scout), but they are so fragile that you have to play very defensively to make sure you never get hit or trapped. And the small size makes it that much harder to do decent damage. The +4 LA is just too much of a delay to build an effective offensive caster, and there's no way they could ever tank.
The absolute best option for a pixie is an assassin, but this breaks your "no PrC" rule. They can completely rock out with the death attack. They can also do a decent job in a support role as a battlefield medic (cleric) or bard, if you're willing to give up anything resembling personal glory for the good of the team.
The real limitation is that pixies will always have jack squat for hitpoints. They do well as a skirmish style class (rogue, scout), but they are so fragile that you have to play very defensively to make sure you never get hit or trapped. And the small size makes it that much harder to do decent damage. The +4 LA is just too much of a delay to build an effective offensive caster, and there's no way they could ever tank.
The absolute best option for a pixie is an assassin, but this breaks your "no PrC" rule. They can completely rock out with the death attack. They can also do a decent job in a support role as a battlefield medic (cleric) or bard, if you're willing to give up anything resembling personal glory for the good of the team.