It is a beautiful clear easy drive. Not many months ago there was extensive construction South of St. George through Arizona. Not scary but it did slow traffic. You get traffic congestion as you go through Las Vegas, but it is slow not difficult, just follow the trucks to be in the correct lane for through traffic. The Cajun Pass between Victorville and San Bernardino is a long steep pull first up then again long straight steep down. The weather in this pass can get extreme, either high winds, snow, rain, or all of the above. But it is a wide well controlled and patrolled freeway so if you watch your speed, drive with care, and take it easy the drive is no worse than any other mountain freeway pass. All in all if you don't try to rush it is an easy uneventful ride. One thing to consider if you are on a time limit, in a car/suv the speed limit in Utah is 80, the 70 in Nevada, and you can maintain 65 in Calif going over the mountain. Not so much in an RV. Given the choice for a vacation I would take the RV.
Happy Trails.