Both Prague and Lugano are great. We were in Prague this last January. Met a Hungarian couple at the Christmas market that were on their way to Amsterdam from Budapest and we had a few drinks and socialized with them. Great fun.
Lugano is gorgeous. Palm trees in Switzerland ? Who'da thunk it. Our favorite thing to do is get some wine, snacks and all day passes for the Swiss ferry boats and ride around the lake all day.
If you haven't done so already, you should ride the "FART" (train) from Locarno to Domadossola. It's a pretty "quaint" train and it takes you through some beautiful scenery and rustic Italian villages before dropping down into the valley where Domodossola lies.
I'm mostly an Alps/mountain kind of person. But if I had to live in a city, it'd be Luzern. The other big Swiss cities don't do much for me, other than perhaps, Zurich.
