That is the route we always take from Tucson. Traffic isn't too bad overall, though it always comes to a stop at some point (It doesn't matter the time of day, weekday/weekend, etc. - it always stops). I can't remember if it's on 60 or 91, sorry. I usually delays us about 30 minutes overall, so not too bad.
There are times that I've considered going the southern route to avoid Phoenix (and avoid using a GPS), how easy is 10 (my only freeway choice down here) to 8 (easy, like you're going to San Diego) to 5. Supposedly, it's only 20 minutes longer (from Tucson), but I have an inkling there would be traffic delays that route as well...