-- No longer a simulation of anything but itself.
-- Perhaps there is fluff to explain it in the PHB, but the key thing is that these powers are not attempting to replicate a real life situation or even something typically seen in Tolkienesque or Conanesque fantasy literature. Instead, they are game rules made because WOTC thinks they make the game work well, no OUTSIDE the game reason. That's a huge shift of logic, at least for me.
--- If D&D 4e is simulating anything, it's simulating computer gaming. Perhaps necessary, but to me, sad.
--- No more resource management needed for the basics.
--- Before Gary Gygax died, one of his complaints about 3e was that it was just too darn complicated and therefore not as open to new players. It looks, so far, as if WOTC has taken that criticism to heart and tried to make a 3e Basic.
-- Valliant effort by WOTC to improve the game by looking at the key issues of correcting the power curve (starting and keeping things in the 2nd-8th level range longer), game play where resource management is no longer key
-- I'm sure it will be fun to play.
-- To me, I'm seeing a game that's something like 60% D&D and 40% new content
-- But in my own campaign, I'm sticking with 3.5e for now.
-- We'll see what's in 4e PHB, but I'm thinking converting is not a real option. I've got 27 years of AD&D and 3.5e content running around in my Greyhawk world, and I don't feel like retconning in total different variants of all the old retired guy and NPC's and semi-dormant campaigns, not to mention adding Dragonborn and whatever lameness awaits in the full books, so I think I'm on my own, just as if D&D had gone belly up and out of business. In a real sense, for old school gamers, I think it has. Good thing I've got like 5 PHB's . . . and I guess if my DMG gets lost or something, use ones will abound for years, as most people will go with the flow and switch over.
-- The only downside to playing 4e and running 3.5e is the brain space and confusion that can result.