|Dennis da Ogre formerly 0gre|
Staying in one class till 20 is always going to be dull no matter what incentives there are to it, because then your character seems like "just another [insert class]".
What is seriously broken with D&D is that WotC found out the way to maximize profits was by upping the number of books they sold. Quality no longer mattered just volume. People's insatiable desire to 'stand out from the crowd' made it easy for them to crank out books and books filled with junky slasses, PrCs, domains, feats, magic items, spells, and races and most of it total garbage.
To be honest if having the coolest funkiest character with the newest features and bling is important to you then I suggest you try out 4e, WotC are the masters at cranking out new stuff on a regular basis. Who knows maybe this time they got it right and they will be able to get the quality part down too.
I'll let you in on a little secret. Cool colorful characters are not a bunch of stupid stats on a page they what you inject into them. Regardless of whether it's a Human Fighter 20 or a Wizard 3/ Master Specialist 7/ Abjurant Champion 3/ Archmage 5. If you need a crutch to make your characters interesting then maybe you should try playing the base classes and focus on role playing instead of being so obsessed with class features.
Some of the coolest characters I've played were generic base classes.