Update on the Swisscom Natel Easy with 4 CHF/day unlimited internet:

I bought the sim at the Swisscom store at the airport (ZRH) with no problem. Was CHF 19.95 and comes with CHF 20 credit (5 days worth of internet).

The SIM works fine in my Tchibo stick. I am in Altstätten SG (not all that far from Liechtenstein -- wanted go the just to burn my UM SIM -- and yes I know it was a Swiss Company :) ) -- not exactly a major metropolitan area. Speed is find for email, web surfing, remote desktop, etc. etc. I get the occasional hickup and have to restart the session, but no more often than with other services.

All in all I am happy. There may be cheaper options out that but for my short trip (a week or so) it has worked fine and I'm sure I'll use it when I'm back in December.

I think those CHF 4/day are the cheapest data offer by far in Switzerland. At least I haven't found anything cheaper.

clarification on the Sunrise Pronto Promo-SIM
 

You may get this SIM at any sunrise shop and also every mobilezone in Switzerland (in real, at every point you can buy a sunrise prepay).

The translation on the 5 days of usage is dependant on the 5 Swiss Francs balance on the card, since the "Flat" fee for calling sunrise mobile (including yallo and cablecom) and fixed net within Switzerland will be charged as 1 CHF daily. The Sim itself will work one year without reload!

BK