I agree. The Ortlieb medium handlebar bag is a keeper. I like the snaps that hold the cover shut. There is the choice to leave them unsnapped which makes it very convenient to get your stuff when you are making short hops between viewpoints. However, if there is a gusty following wind it can flip the top open so then it is good to use the snaps which have never let me down. Actually, I tend to use the snaps out of caution in case of some mishap so that my stuff doesn't end up all over the road.
The map case is great--Very waterproof and easy to access although it, too, can get windblown by a following wind and sometimes needs to be relegated temporarily to a pannier.
The bag comes off the handlebars easily when desired.
I have not had anything get wet during rain but still use baggies for my cell phone, pda and camera.
The bag can hold a lot of stuff...I hate to think what the large size would end up weighing. I have mine mounted on a separate stem and sawed-off handle bar below the level of my main handlebars. This gives me more room on the main bars for lights and cyclometers and also lowers the center-of-gravity a bit.
It's hard to imagine touring without one.