Is this discussion really limited to 4e or should it be widened to running non-combat sessions in any edition?
I posted it in the 4e forum because I'm a 4e GM, and Chris Perkins was posting about 4e games, and 4e is, at least in my view, an RPG that makes
combat as a means of conflict resolution fairly central to the game. (I've italicised the whole of that phrase deliberately - I think 4e is best for running
meaningful combats, where the stakes are something other than just win/lose.)
I'm happy for it to be about other editions/games, but for some of them the question is less salient. Gygax's AD&D, for example, focuses less on combat than on treasure-recovery, as the main site of conflict and achievement; and Classic Traveller could easily be a game full of combatless sessions.
I played in one tonight, and while the roleplay opportunities were a nice change of pace overall (usually this is a two-battles-a-night game), it got to be a trifle on the dull side after three hours of talking in character.
A non-combat session isn't there to waste time with nothing more than improv characterization. It's there to learn vital clues, advance important relationships and persuade NPCs (by means fair or foul) to do what you want.
I'm with KidSnide on this one. Non-combat doesn't just mean "talking in character". Most of my players don't do very much of that, and the non-combat session I described didn't differ in that respect. There was planning, discussions of who was doing what in the various skill challenges, the back-and-forth of the exploration, etc. Even in social interactions, like the social skill chalenge, meeting the dwarven smith, and meeting the patriarch in the parade, the players use indirect as much as direct speech - describing what they do and say, as well as (sometimes) actually doing or saying it.
As GM, I think I use more direct speech than anyone else at the table, even when that requires hamming it up or raising my voice a bit, because I take part of my job being to create some atmosphere - especially in a social scene.