It's all good. Every square mile of it. The entire coast is an amazing place and a great drive - refer to all the other comments for details. :) Very busy in the summer of course so book your CG sites way in advance...
A drive up (or down) Mt. Hood hwy 26 east of Portland is excellent scenery and will take you up into the Cascades. You can take 35 northward off 26 and drive up towards Mt. Hood and visit the historic
Timberline Lodge at 6,000 ft elev. Very cool. Mt Hood is the 2nd most climbed mountain in the world with a peak elev. of 11,250'. The town of Government Camp is interesting.
The coastal area from CA to WA is a narrow strip of green (everywhere you look!!) and when you get up into the Cascades and go east, it's a totally different world. North/south highways like 395 & 97 are fantastic scenery and great drives. The Bend area is very nice.
If you want to see some mountain passes, there's over 300 of them in OR with a few over 8,000' elev. If you like super-twisty roads, there's plenty of them and lots in the mountains and some with sheer dropoffs alongside. Personally, I can't get enough of them - 119 and 20 & 34 (IIRC) west of Bend come to mind.
The southern portion I-5 is a good drive and the drive up through Grants Pass is fun - long and steep-ish. You can go east from Medford up into Rogue River-Siskiyou NF. Lots of great CGs there. Not many RVs use I-5 and not many CGS along it.
Lots of charming, picturesque & interesting historic towns around OR. - Ashland, Astoria, McMinville, Silverton, etc., etc. Too many to list so do some googling!
Don't forget to report back after the trip. ;)