In 3ed playing at level 1 is different than playing at level 6, or level 12 or level 20. That's a GREAT feature! Different challenges, different types of resource management, different ways to solve obstacles etc. It's especially different to play a spellcaster: at low levels it's all about casting the few spells at the right time, at high levels it's all about stacking your buffs and protections in the most convenient way. I admit that I always have lots of problems running a 3ed game beyond level 15th (or even earlier), I'd like to think that given time I'll manage it tho... But after we go very high up in level, it doesn't feel bad at the end of the campaign to go back at 1st to start the next, because there are challenges which are unique to low levels, and they don't become too easy even for players that have played the high levels.
I like the way it is, because it's like having 3-4 different games in the same ruleset.