We decided months ago that we're gonna bend over backwards to interop with everyone. We want you to be able to open Tidepool to gather photos from your camera, open iPhoto to remove some red-eye and rotate a few, open Tidepool to do some tagging, open Photoshop Album to see those tags, etc. We'd rather compete on merit than hold our customers hostage. Big Fractal Tangle: all-hands interop
I honestly don't believe that lock-in on formats/non-interoperability is a good long term strategy.
I'm still struggling in the search for a good contact/calendar/project management tool that works for multiple people and is cross-platform. We're trying out Basecamp. I had given it a try quite some time ago, and felt mediocre about it. It seems to be working out better this time, especially the way it integrates with iCal (tasks and calendar events) and having your own custom RSS feeds for notification.
Silver Orange's Intranet looks really good, too, but the online demo doesn't give me enough of a feel for how well it might work. And of course I haven't had the time to ask for a more complete demo.