My wife is a school bus driver and she drove our class A for the first 30 miles. I took over the next day and drove it 250 miles home; mostly on the freeeway. This was almost 2 years (and 3500 miles) ago and I am still not completely relaxed in the rig unless I'm driving it on a wide road or the freeway.
The problem for me has been a lack of good references; no hood ornament, for instance. So I use the mirrors to see the white lines on each side of the coach as we pass along between them. This worked out remarkably well. However on many sharp corners in towns and cities the lines disappear and then all you have is experience.
It gets better. And at least I don't have to deal with all the kids. :)
Craig