Hussar
Legend
Personally, I see nothing retro about 4e. It seems to me that the game has nothing in common with BECMI.
4e has a highly tactical combat system that requires the use of a battlemat. The characters are highly customizable and begin 1st level as already quite competent... the list could go on.
4e is a very modern game.
Oh sure, it's pretty difficult to do a point by point comparison between a 64 page rule book and almost a thousand pages. Heck, even if you include Expert Rules in there, you're still way under any single 4e book. So, yeah, there's gonna be some mechanical differences.
But, as others have pointed out, stylistically, this looks a LOT more like Basic/Expert than 3e. Monsters that are simply things to be killed with the expectation that the DM will build his own world to explain them. Kinda like how Keep on the Borderlands was a very basic framework from which the DM was expected to fill in. 'Course, there is a difference there as well - this time 'round you're actually given some pointers on how to fill in the blanks. Basic/Expert was a little light in that regard.
Narrow classes. Granted, they're not as narrow as Basic/Expert classes, but, there is still the expected path laid out for you.
On the point about "competent 1st level characters". A 1st level fighter in Basic D&D has plate mail and a shield, giving him a 2 AC without any Dex bonus (Plate is 60 gp, you roll 3d6x10 for gold - buying plate, shield and a sword isn't too difficult). Anything you meet at that level is going to need an 18 or so to hit you. So, while you don't have a lot of hit points, nothing ever really hits you too much.
Add to that the expectation of 6-8 PC's, plus hirelings/henchmen/cannon fodder, and you'll find that Basic D&D characters are actually pretty sturdy.