Well, I've only built and run two adventures with 4e. I'm still wrestling the 3e rules out of my head. Like deciding ahead of time what a magic item is, since there's no random chart to consult mid-game. (I've since added an excell sheet to take care of that for now)
I find that the pacing does work itself out quite nicely in 4e. And I have enjoyed the new thinking in encounter design. Not having to assemble a statblock for a monster also helps greatly. So far as a DM 4e is nice and in practice runs a lot closer to my usual style. So the adjustments are simply breaking old habits. Of course, YMMV
Well I am waiting until everyone has the difference between "Burst" and "Blast" down before I try running a higher level game.
I have run a couple of encounters myself just to see how a level 19 Great Weapon Fighter goes against a Level 19 Umber Hulk I adjusted up. That was slow and cumbersome since I was trying to read every rules that came up to make sure I had it all figured out. I certianly hope things go faster when I get a chance to run that in the future.
All things considered, the only part I'm not enjoying about 4e is my inner grognard hates the simplification. I have a little masochistic voice in my head that feels that I should grab a pile of d8's when a random monster comes into play and roll his hit dice right there at the table with the players crossing thier fingers for bad rolls. But the rest of me enjoys simply grabbing a monster stat block from the MM and plunking a monster onto the table and proclaiming, "Roll initiative, he's here and he's attacking."