Oslo to Copenhagen boat ride (overnight)?

I did Copenhagen to Oslo a couple years ago. It was nice to fall asleep in a fairly comfortable bed and wake up in Oslo. I'd recommend it but it's not glamorous or anything. Definitely low frills :)

It can be a pleasant way to get from Oslo to Copenhagen. The trip through the Oslo fljord is fairly scenic and the views of Kronborg Castle as you sail by Helsingør is also very nice.
It can also be a bit of a booze cruise. I answered a question about it a not long ago in more detail
https://community.ricksteves.com/travel-forum/general-europe/scandinavian-cruise-question

I will be going Oslo to Copenhagen this fall on the overnight boat ( DFDS ) . Information here http://www.dfdsseaways.us/

Yes, Rick's Scandinavia book gives this route a quicker description (pages 131-2 & 285), including "not as swanky as the Stockholm-Helsinki cruise." Or, you can fly for $100 on Norwegian airlines (I see it displayed as $50 plus taxes and fees).

When planning my trip I considered the overnight ferry. I decided to fly from Copenhagen to Oslo. The flight last about 1 hour and cost $58.00 per person on Norwegian Airlines. Of course I do have another night in hotel in Copenhagen. I will be just getting back from a 7 day cruise and did not want another night on a boat.

We're flying to Oslo in August for $71 on Norwegian Air Shuttle. Easiest way to do it.

I did this a few years ago, so not sure if it is still the same. At the time it was a nice way to get from Oslo to Copenhagen. There was a nice meal, a few different entertainment areas in the evening (bar, music type) and some nice scenary to look at for awhile. I slept pretty well and woke up in Copenhagen. I enjoyed it.