Personally I've looked at various of the canned modules, but I am just one of those people that really LIKES to make up adventures, so I haven't run any of them. Plus I kind of think there is an overemphasis on combat in the ones I've looked at. If most of what players face is combat encounters, then they tend to start character optimizing for combat and I'd say things get less interesting myself. It can get a bit absurd at high levels.
I think the adventure and encounter building guidelines in the DMG don't really emphasize the need to create interesting terrain and environmental elements which allow for maximum use of skills in combat. You can get away with SOME encounters that are sort of old-style "Monsters in a Room" type stuff, but I'd only do that for fairly trivial encounters or just once in a while for the sake of variety.
DMs should NEVER (again unless there is a real story reason for it or its part of a tactical concept for an encounter) have the old proverbial 20x20 room with some Orcs in it and nothing else. The area will be far too small for a decent combat and it will just be a toe-to-toe boring slugfest. 4e combat is all about moving around, hiding, using skills to perform stunts, etc. An encounter area should thus be large enough for the combatants to move around and flank each other, etc. Ideally it should have some terrain that presents a tactical challenge, like the orc archers can only be gotten to if you take a long way around a side corridor, or climb ropes up to a balcony, etc.
Personally I think half of the encounters should be skill challenges, roughly. Some can mix both, so you would probably have more than 50% being combat as well. The skill challenges of course can't block progress on a failure, but they should either reward success with some extra benefit or result in some loss of resources like healing surges on failure. Make SURE the DM gets the DMG errata since the skill challenge math as printed was really completely out to lunch.
Mostly, 4e is supposed to be cinematic. It is like a simulation of an Errol Flynn movie or Raiders of The Lost Arc than anything else. When building encounters imagine you're making a movie set. Everything serves the story and all fluff is just skin deep, change it as you like.