Okay, a couple of contributions to be weighed and/or ignored...

Personally I think Crater Lake is a lovely place, but I put it into a category of National Parks that I'd call something like, "Don't miss if you're nearby." Other candidates for that category include Badlands NP, Grand Teton NP, Joshua Tree NP, and a few others (including our own North Cascades NP.) Basically, they are great places to visit en route somewhere else, but not - again, just IMO - as destinations on their own.

In the case of Crater Lake, it's a really long drive from Portland (or pretty much anywhere else except Roseburg or Bend) and it pretty much kills a day in each direction with scenery that's okay but not life-changing. Once at the rim of Crater Lake, it's a grand view that you can accomplish in a couple of hours on the rim drive, but then, unless you want to go hiking, or have some special aim, like a photo every hour for 24 hours to show the changing light, that's about it. The Crater Lake Lodge has been updated in recent years, so it's no longer the disgrace it was, but it's still way overpriced for the amenity level.

So you can decide how the "Is it worth it?" question plays for you. Fortunately, around Portland, you have an embarrassment of riches that could take the place of those days/hours.

Portland itself is a very fun and funky city, with lots of urban distractions to savor - great food scene, lively arts, great parks, microbrews and the great McMenamins hotels, bars, and restaurants, great shopping (no sales tax...)

Add to that the Columbia Gorge, Hood River Valley, Mount Hood and the Willamette Valley wineries... and the destinations and things-to-do list starts getting unwieldy.

Example of a killer autumn day: Start at McMenamin's Edgefield, where you've spent the night decompressing from a transcon trip, 10 min. from PDX but definitely in the country. Drive east from Troutdale along the Historic Columbia Gorge Highway, past the Crown Point Vista House, Latourelle and Multnomah Falls, to Hood River. Grab a beer or some coffee, or an early lunch at one of the brewpubs or similar, watching the windsurfers on the river, then head up the Hood River Valley toward Mount Hood. In October all the orchards around Hood River and the valley ought to be gorgeous; it will probably be harvest time so plenty of apples on offer.

Up the mountain to Timberline Lodge for a look around, a walk and a late lunch or coffee, then you can head back to Troutdale or Portland via US 26, making a great loop out of the day (or just retrace your steps and get surprising views of Mount Adams as you travel downhill through the Hood River Valley.)

The next day, if the weather's decent you can do a day trip up to Mount St. Helens, another volcano (like Crater Lake) but one still doing Volcano things. Around 90 min. each way from Portland/Troutdale to the visitors center. Or head over to the Willamette Valley for some wine tasting, or if you're feeling energetic, take the north shore of the Columbia downstream to Cape Disappointment and Ilwaco on the Washington side of the mouth for some great rock-ocean-lighthouse scenery, then cross the (awesome) bridge to Astoria, then back to Portland on the Oregon side. Gorgeous, historic route.

So that's killed two days in day trips based out of Portland. More doing, way less driving.

Then to get from Portland to Seattle, and assuming you can get away around noon, don't take I-5, which is boring and probably really slow when you get to the military bases south of Tacoma and through the Tacoma/Seattle traffic zone.

Instead, head east back up the Gorge (you can take the freeway if you've already taken the "historic" highway) to US 97 near The Dalles. If you have extra time, spend an hour at the Maryhill Museum for a surprising blast of culture in the sagebrush. Turn north on US 97 and go through some fantastic "old west" landscape over Satus Pass and through the Yakama reservation to Yakima - again, more vineyards and sunshine, then connect to I-82 and eventually I-90 and come into Seattle from the east, through the mountains that ought to have good fall color at altitude.

This route takes around 90 min. longer than the freeway, but it's so much more scenic and interesting that it's ridiculous.