There is a lot scenery to take in and the roads are all pretty good quality so not much to worry about.
I drove around 80 mph if not more basically the entire way. Didn't have much problems. I drove with some friends who were visiting for the first time, so we drove from San Jose on CA-1 up to Leggett before getting back to I-5. The goal was skiing in Whistler so we didn't stop much. We did the border crossing at Peace Arch, spent I think 15 minutes to get through. Coming back was more of a hassle (US immigration was way more strict--a friend of mine actually received a paper I-94, hadn't seen one of those in a while). Only thing I forgot was Canada uses metric (haha) so make sure you are not driving 80 mph in a 80 kmh zone
There is nothing you need to stay away from if you mean from a safety perspective. Just be sure to bring a raincoat for Seattle. I don't think there is any way to screw up the trip really. It's all very beautiful up there and the people are all pretty nice with none that crud we have in and around the Bay Area.
Don't forgot those passports
