I came back from Oregon last month via I-15 and 89A. In past years I remember horrendous construction in the SLC area, but this time is was a breeze. Really, I was shocked at how easy it was.
You have to get onto 89A at Kanab instead of staying on 89 through Page, AZ because just south of Page there is a major landslide (happened last Feb.), so a section of 89 is closed. You meet up with 89 again south of the landslide. Hwy 89A has a climb with some twists and turns up to Jacob Lake, then downhill the other side of Jacob Lake. But the road is good and no big deal. Much easier, in fact, than I remember from years ago when I drove it. Maybe I just have more experience now :)