I like 4E a lot, yet:
This
Eliminate tactical movement tracking at least to the point of not having to go to the battlemaps for every minor encounter: an ideal system would have a quick way to switch grids on/off for when a DM needs to make up a quick battle, or a particular encounter with a very large or very particular battlefield ill suited to combat grids, this would make battles not so legoland style;
This
Much more fluff for monsters. Many of my homebrew adventures sprang from the flavour text of past MM, much more evocative than today to the fertile mind;
And this
Magic has GOT to be tweaked to make it feel more like magic of earlier editions
Magic has to feel, well, magical, to the point of being different from the other non magical things.
For monsters and NPCs, the actual system is not a bad thing at all: I managed to obtain the result above by giving them what old edition style spells they needed. For instance, my arachnomancer escaped the party by casting during the battle its
rock to web and
spider climb illegal, tricky, invented and beautiful spells, it was really like old times. No player complained, as they no longer know what monsters really do

, I love this side of the new monsters. If done cautiously and without abuse, they'll never know if you or the Great Designers made those spell powers. For PCs, much more difficult to accomplish and severely missed.
I also think monsters HPs and defenses are too high, but this is simply fixed by resorting to clever suggestions in this same forum. PCs HPs are too many too, but a DM has his higher-level, HP-weakened monster friends eager to take care of this
