Any advice for Oslo?

Copenhagen is indeed ace, Oslo is too but I prefer Copenhagen.
Go the park in front of the Royal Palace and hang out there for a bit while people watching and reading a map. The area behind the Palace is quite cool, loads of little boutiques, cafés, bars etc. Has a kind of Notting Hill/Westbourne Park kinda vibe

+1 to this. And check out the new opera house at the harbour.
No faxengers spotted when I was there. Saw lots of mtb'ers though and a few roadies.

And bring lots of cash. Feckin expensive.