Norway in the nutshell
 

Is this tour worth it if I'm already travelling by train from Oslo-Bergen, and by Hurtigruten from Bergen-Tromso? I imagine the contrast between the views from land and sea is already covered by the train/Hurtigruten route and as such, the Norway in the nutshell day trip may not be worth the time and expense. Thoughts?

NIN is just a package of individual tickets. By not doing it, you will miss the train ride down the fjord, the ferry ride and the bus ride up to the main train line. I think that you can skip all that unless you are a train fanatic. Especially if the Hurtigruten stops in Geiranger Fjord.

Seems to be the highlight of most peoples trip to Norway. You could do it on the way between Oslo and Bergen so doesn't add any more days - no need to do it separately as a day trip. Save money by buying the NSB ticket Oslo-Myrdal - Flåm (or Bergen) in advance with minipris non-changeable tickets available 90 days in advance - https://www.nsb.no/en/

What Michael said; we drove from Oslo to Voss, stayed at Fleischer's Hotel [Grand old hotel].

We did the NIN and loved it!

We then drove back to Oslo. Sorry we didn't get to Bergen as we were in a bit of time constraint.

I was less than impressed and I like trains. The stop to view the "maiden in the mist" or whatever was hokey. I did think Flam was quite pretty but ready to leave after one hour. The boat trip through the fjord was pretty. The best part was the bus ride back to Bergen. Bergen was worth a day.

Glad other people liked it.