My wife and I just returned from travel to several countries. We flew into Oslo and did the one day Nutshell tour to Bergen so I'll share some brief comments as I was benifited by several posts on this baord prior to our leaving.
The Nutshell tour is wonderful. The first few hours on the train out of Oslo has no real dramatic scenery but it does get spectatular! The transfers are easy unless you are lugging a lot of luggage in which case I'd sugest a proter service. Myrdal to Flam rail is fantastic and the cruise through the fiord is just spectacular. Try for a bus taking the old road to Voss as it is quite dramatic, new road goes through a tunnel.
Bergen is lovely and quite walkable. As a US visitor you may find it interesting to have whale meat on a menue (I liked it, wife says NO) Reindeer too.....and baby seal skins for sale but US customs may not allow them back, we didn't buy any.
I must add, as has been posted here before it is VERY expensive against the US dollar. 59 NOK ($10 US) average price for a beer at a pub but you may find some for less for take away at small grocery. We paid $8 US for a small order of not very good garlic bread at Pepes Pizza to go with our 2 $10 beers. And fish and chips on paper plate outdoors at the fish market was about $12 US.
We chatted with some local working people and found that wage laws there are complex but favorable for labor..... were told that the most minimal wage for those under 18 (more as you are older) is 114 NOK/hr or about $19 US with mandatory double time on weekends and other increases after 5 PM etc. So prices seem more reasonable on the local economy, it is just that the worm has turned and the old yankee dollar isn't king anymore.
Well, those are the things I would have wanted to know before I left so I share them for what they may be worth.