I'm not too concerned about the official rate of advancement in 4e. IMC, advancement will be somewhat arbitrary. PCs will level at a fairly regular, but much slower pace than the RAW. I use a somewhat vague system wherein short scenarios equal 1 point; medium scenarios 2 points; long scenarios 3 points; and really long scenarios 4 points. Characters level after accumulating 4 points. The PCs never see this system in action. After a scenario ends (and at no point during the scenario), I award 250 xp per character level, per adventure point to each character in play.
I've been using this system in 3e as well. I had to house rule level loss away (I've hated it since 1978), and I had to give 10% extra xp to cover things like crafting and casting spells with xp components.
My group prefers play in what 4e refers to as the heroic tier. If the sweet spot is extended as promised, we may enjoy the paragon tier as well. The playtest reviews we've seen that deal with the epic tier make it clear that most of us will probably not like it.
We like much slower advancement (similar to 2e) and a lot of downtime between adventures. This more than anything else has led to our intense dislike of Adventure Path type campaigns (although it took us Shackled City, Age of Worms and Savage Tide before we put it in those terms).