Interlaken Ost - Zweisimmen

I think I would do it during daytime. The ride along lake Thun, Spiez, and then the Simmental is nice. I mean it is not breathtaking like a ride to the Gornergrat but the scenery is great. You see some big and impressive old chalets in the Simmental.

The scenery on this stretch isn't "jaw-dropping". It wouldn't be a crime to travel after dark.

I've done that route in the dark to dawn on the way to Montreux. I'm probably spoiled because of frequent visits to Switzerland and the Interlaken/Thunersee/Spiez area. I tend to agree with both previous posts. Its not stunning but if it were my first visit to the BO I'd be impressed. As I said, our night trip was very early in the morning. What impressed me about the journey was the glimpses of the large (by Swiss standards) buildings on the farms in the Simmental and as we went west the change in the language spoken by the schoolchildren. We always take the local Swiss trains on the scenic routes rather than the named trains with the hermetically sealed windows and only tourists, often in groups. The trains take the same time and pretty much same stopping patterns but are the same ones used by the Swiss going about their daily life. We enjoyed listening to the children all speaking in Swiss-German then, for a short while, a mixture (sometimes one speaking in German and being answered in French), then them all speaking French. We found it really cool. The children at that time of day use the train as a school bus. BTW, of course being morning, the day was getting lighter as we went...

Nigel: Well spotted. It is indeed interesting to experience the subtle and almost invisible boundaries in Language/religion/architecture along that line. As you noted some of the kids you saw (probably in the Canton Fribourg section of that line) are "Bolzes". Completely bi-lingual and switching constantly between French and Swiss German (Seislertütsch to be exact) during a conversation.