Several MMORPGs that I’ve played have had a system for continued character advancement after the level cap. Although the details differed the overall aim was the same, to give the player something to work towards after the character has stopped leveling.
I’ve just read that Neverwinter will be adding a simple version of this concept with Module 3. From that patch onwards characters will continue to accrue experience points which, when the bar is full will grant a power point instead of a new level. Power points are used to unlock and improve your various class at-will, encounter, daily and passive powers.
This will allow you to unlock more powers on your character, but the standard limit of slotted and available powers of each type remains the same. So there’s not explicit power creep in this, just increased flexibility. I’ll review the implementation when the patch has been released but I like the sound of this version of continued character development.
Other games have similar systems: Everquest 2 has Alternative Advancement, Rift has Planar Attunement and Guild Wars 2 has continued skill point gain. Some systems are more complex than others and more unbalancing (e.g. AAs in EQ2 can give low level characters ridiculous power). But having some form of continued progress for your character is definitely a good thing in my mind!
Do you have a preference on whether there should be post-cap progression for characters, and on what form that should take?