No hassle in Switzerland, but do remember to take Swiss Francs. The chances of finding somewhere that takes Euros is slim, as I found out in Geneva last year.
If you use the autoroutes in Switzerland you will also need to buy a pass before you go on them and as they only sell annual passes they work out expensive. Not a problem if you are planning on the scenic route though.
You buy the pass at the start of the motorway theres a old looking guard post which is the office, the pass will last a year worth getting if using more than once but not if only passing through stick to Italy, some lovely sites up in the mountains in Northern Italy