I just read that the ATM's in Switzerland just take Mastercard. Of course, my ATM card is a Visa. Can someone confirm or deny?

I see no evidence from any website this is true. Swiss ATMs support the banking networks that we have in the U.S. Anyone else?

Not true. I have a Bank of American ATM attached to my checking accout with a Visa logo on the card, works fine, four trips to Switzerland.

You do want to be sure and have a 4 digit (numerical) pin number (not six and not letters because the keypads aren't necessarily the same).

No, the statement is not true.
I can however understand how that story might have gotten started.

There were at one time a few banks in Switzerland that accepted only MC or only Visa. I encountered that situation 1998 when I was in Lauterbrunnen and later in Saas Grund.
The first bank I visited in Lauterbrunnen accepted only MC ATM cards, and the bank down the street accepted only Visa.

By the time I visited Saas Grund, I knew which bank to visit, so there was absolutely no problem.

In the larger towns and cities, the situation did exist then, or now. For example, we were in Luzern, and the first bank I walked up to accepted my Visa ATM card.

I have been back to Lauterbrunnen since 1998 and found that I had absolutely no trouble using my Visa card.

I don't see any reason to be concerned.

I do, however, out of habit, carry a few American Express travelers checks with me, just in case. I regard them as a back up and have no real intentions of using them. But there is always a chance, remote as it is, that the ATM could be out of order.
So I have my financial safety net that I have used exactly twice in many trips.

The main thing to look at is what systems your card is good on. For example my card is not a Visa or a MasterCard but is a plain ATM card. I can use it at any ATM on the Plus, Pulse or interlink systems.