I was thinking of doing a Norway in a Nutshell trip that Rick Steves has in his book; a one day round trip from Oslo in early July.

Is the trip worthwhile, or is it overrated?

Thanks!

We did it as a day trip from Bergen. We had spent the previous 12 days on the Coastal Voyage and thought we might have seen enough fjords but we found it a very relaxing day though it would be much longer for you doing it from Oslo.
We purchased our tickets from the tourist office the day before and it just went like clockwork. Do a train journey, a bus trip, a ferry ride and back on the train with stunning scenery thrown in! Just remember which bus is yours after the stop at Stalheim.

Do a search on here and you will find some differing opinions. Would we do it again - you bet!

It was definitely worth it to me.

I can't say if it is worthwhile or not as I have not gone on my trip yet (early July also) but I am looking forward to it and based on reviews and their website it looks like a nice way to travel through the country.

Type in the Search Engine NIN and you should get some more reviews. Also, if you haven't yet, they have a website worth checking out.

One of the most fantastic trips i've ever done in four decades of European travel.

Would not do as a day trip from oslo however but stay in Bergen and do it as a day trip from there

there are overnight trains Bergen-Oslo however

I would say it's absolutely worth it and that it is not overrated. However, you'll have to decide on the best itinerary to take. Consider spending the night at the Stalheim or better yet, take the ferry across the fjord to Balestrand. That leg of the journey was more spectacular to me than the trip down the Naeroyfjorden. You could spend the night at Balestrand and take the ferry back to Bergen the next day. Also, be sure to get reservations for each leg of the trip. We were told by some that we did not need them but we absolutely did. When you get on the ferry it is a mad rush and if you don't have reservations and/or a ticket it creates a traffic jam. Have a wonderful time!

For a scintillating picture of Norway's largest fjord and also of the Bergen Railway (Oslo-Bergen) which i rank up in the top five scenic railways in Europe:

http://www.norwaynutshell.com/default.asp

The ticket we purchased was all in one, we didn't make any other reservations and no looked at our tickets apart from the train back to Bergen which I think was the only time we had to sit in an allocated seat.