While I might use TAF's if they were available, I don't think it's high on MY priority list. The TAF for most anywhere on the route of flight is easy enough to print out before the flight, and generally isn't going to change that much between stops. For weather, I'd prefer the active weather RADAR, similar to the XM or ADSB sutff, but I imagine that's a ways off. For maps I'd like to see the Terminal Area Charts, and specialty charts like the Grand Canyon.