Before I comment, I should point out that I haven't actually started DM'ing it yet. That's next week
From my prep work, though, I think edition doesn't play a big part in how easy or hard it is to DM. From the module standpoint, I think it's definitely on the hard end of the scale to DM. It has a lot of things going on at once and a lot of things to remember. I'm finding I have to create a lot of visual cues to remind me of certain little things to avoid burying my head in the text for half the game.
Things like tactics changing from round to round, or complex interactions with the environment or NPC's, or changing conditions of battle, or added terrain features, or additional combatants or just complex tactics that require being on the ball, certainly make it a challenge to DM.
Of course, this is what also makes it interesting. Of the six combat encounters I've prepared for so far, none are very static or simple slug-fests.
On the mechanics side, there is some wonkiness in the 4e monsters. I've changed a fair few of them to fix what I perceive as being either under or over powered, or simply just dull. I think a lot of the monsters could've been made more dynamic or interesting. I definitely get the sense that these monsters were created early on in the introduction of 4e as they seem to be very reminiscent of their 3.x counterparts.
Then again, I haven't even prepped the entirety of the first module so take my opinion with a grain of salt. For the most part, I think you'll be fine given your experience. Just do your prep work and have lots of sticky reminder notes
