We arrived in Mürren today. We opted for the Swiss 8 day travel pass. I used the spread sheet, and had I booked 30 days out with super saver fares or day passes where available, worst case, we broke even by the time we added the Shilthorn and Mount Rigi. But to have the flexibility of hopping on whatever train you want is awesome. And add in additional transportation at no cost us well worth it.
After checking into our hotel in Mürren, we decided to take the train and tram back to Lauterbrunnen to wander, and have dinner. This time of year the temp difference between Mürren and valley floor is big. So we had dinner outside on a patio in Lauterbrunnen. Was nice to hop back on the train and not feel we were wasting money. We even considered going to Shilthorn this afternoon, (already planned for tomorrow), but clouds rolled in.
We ended up not going to museums as planned in Lucern since weather was way to nice.
We booked directly from SBB website. Had problems with Capital One Card (even after calling them), and also with Chase Visa, but transaction worked after I was transferred to Visa to confirm charge was valid. Be prepared with extra time when you purchase the passes.