We did a 10 day road trip through Switzerland in August, and I am happy we had a car (cost 450CHF for 11 days rental)
I've gone to Switzerland by train (with an Interrail pass) before and with a car it was much easier, faster and efficient (and probably cheaper), but we also avoided big cities, and made sure to stay in places with free parking. Even in the summer, traffic was not an issue anywhere, and the driving culture is excellent in Switzerland.
After landing in Zurich, we visited Liechtenstein, Locarno (and via Verazsca/Lake Maggiore), Zermatt and mountains (stayed in Tasch and trained in - get Zermatt pass for cable cars if dont have a rail card), the hot pools around Brig on a rainy day, then onto Interlaken are (Interlaken, Lauterbrunner,Murren, Gimmewald), Bern, Gruyeres area and Montreaux. Flew out of Geneva