Any post mentioning heavy traffic or bad roads is likely to generate 'you think that's bad ...' responses.
I've only driven I84 through Boise once, when I was pushing on to Utah (and spent the night in Twin Falls). Other times in the area I bypassed the city by going through the mountains to the north (Stanley). And one time I was seeking out wild-stuff along the east side of Oregon, and only stopped in Ontario for gas and groceries. And later drove into the SW corner of Idaho (Silver City) from Jordan Valley
I was wondering whether ID 78 was any more scenic, so took a Streetview, and my first try turned up this passing shot - of a triple trailer truck loaded with hay. But no other passing traffic for miles.
https://goo.gl/maps/GMMwoJdkDaR2I can see myself taking 78 across this part of Idaho, not so much to avoid the freeway, but because I like driving across miles of nowhere.