I really like the basic concept behind proficiency. I can understand the concern of others here, and its certainly valid to voice them, but we don't have enough context for all the other modifiers (skills, stats, items) to see the full range in skill values. And there clearly are other modifiers that will increase this range so that it won't be simply a 5 difference.
The skill feats is where it will allow characters to shine in ways other than just a higher bonus, which is better if done right. Agree that Paizo need to be careful to not lock tasks anyone trained in a skill should be able to perform behind expert/master tiers.
Scaling proficiency in skills means that tasks untrained/trained characters could reasonably attempt at Level 1 can still be reasonably attempted at Level 10. The expert/master tier characters with more skill points and skill feats invested are still going to be much better in bonuses and additional tricks they can pull off. So I am very happy by what I have heard of the change to date!