I second 2d combat. In 3.5, flight was relatively easy to come by..not so in 4e....even at higher levels of play.
Air Walk, Mass Fly, a Wand of Fly....any and all of these were often essential to higher level play as all of the monsters flew.....the monsters still fly in 4e, but it is much harder for the party. I also think the lack of iterative attacks further exacerbates this ....a 15th level fighter in 3e with no archery feats still gets 3 attacks with a longbow....which can produce a credible threat, or at least something that can not be ignored....a Fighter in 4e making basic ranged attacks is a joke.
Fireball: You take the most iconic spell in the game and make it a horrible daily that is not chosen anymore. WTF!
PHB1 vs PHB2: the polish in PHB2 is clearly evident, while PHB 1 many of the iconic classes are just not given the treatment they should.
Utility powers/Non Direct Damaging powers: my fondest memories of all prior editions are creative uses of non damaging powers. Such as casting Grease on a cliff face as enemies are climbing up, or using Stone Shape to change the battle field and create a choke point, or using Lower Water to prevent an Water Elemental from using Whirlwind in a sewer pipe.
4e lacks that type of magic and wonder, and non damaging spells are often either nearly unusable due to the writing (Grease I am looking at you), or just dominating (the Wizard Avarice daily (exact name escapes me right now).
Magic Item usage per day depending on level: lame...just lame and I suspect is also the rule that is probably most ignored or forgotten (like weapon vs armor type penalties in 1e)