I'll leave it to the pros to break everything down but I just wanted to comment that although I too don't often use longer focal lengths, it's awfully handy to have it around the few times the occasion calls for it. I'm not sure it'd be all that beneficial to move from one kit lens to another and lose that bit you're not sure you'll miss. I say this because I nearly sold my 18-70mm as I hadn't picked it up since I bought my 35mm over a year ago. But today I really, REALLY appreciated having the wider angle. In urban settings it's handy to have the zoom available for those sneaky shots. Food for thought.
