I'm personally not a fan of on-line design programs, I'd rather be running it right here, not to mention sharing only what I want to share. 
Too many web sites have "shared" stuff that clearly wasn't supposed to be shared in recent memory, I'll stick with desktop based PCB layout.
Tom, that's where the 3D view comes in handy. If you make sure the dimensions of the parts are correct (you can tweak them), in the 3D view, they usually fit when the boards arrive. I've had issues a couple of times with hole sizes.
The nice thing about components is once you've done a bunch of boards and perhaps developed a bunch of your own parts, you don't have to do that much searching. If I want the Panasonic capacitor I use in a number of designs, I just open up that design, copy the part, and paste it into my new design. All it's characteristics come along with it.
