It's becoming more popular to get a morgage in swiss francs. It's especially becoming common in Austria. The reasoning behind this is that the base interest rate set by the swiss national bank (whatever they're actually called) is significantly lower than the ECB rate. It is also assumed that the value of the Swiss Franc will remain relativly constant relative to the euro. Of course this is just an assumption and no guarantee
The danger of taking out a morgage in a foreign currency is always that the value of this currency will rise relative to the value of the currency you are earning in (or receiving rent in) to pay back the morgage
So, for example, say 1 CHF = 0.6 EUR and your morgage payments are 2000 CHF per month (1200 EUR). Now if for some reason the value of the euro were to fall relative to the franc so that we now have 1 CHF = 0.7 EUR, you still have to pay back 2000 CHF per month, but this is now 1400 EUR. So if you're using your euro earnings to pay back the morgage, then you are an extra 200 EUR out of pocket/
If you are renting out the property in a non Euro country, e.g. Poland, and dependant on the rent from your tenant to pay back the morgage, then if the Zloty were to fall in value relative to the Swiss Franc, then you have the same problem.
There is also a danger that the Swiss interest rates may rise higher than the ECB one (or the rates of your country). IMHO that is secondary relative to the currency fluctuation risk.