Best level to play?

[molonel]

9th.

Spellcasters will have access to Teleport and Plane Shift which opens up whole new vistas of adventuring possibilities.

Fighters are tough.

Rogues are skillful.

But not so tough and skillful that creating combat encounters becomes a part-time job that requires a level of mathematical aptitude that daunts even an accountant.

 

[Wombat]

I'd say 4-8th are my fave levels. Below that you are still fragile and "levelling up in the valley"; above that, things get tricky for logically keeping a group together (and for them not taking over the kingdom).

Above 15, I get bored with trying to make any of it even vaguely believeable.