Never driven myself but I have family that way who have driven up to me, 3-4 hours on a steady run.
I used to be a ski instructor many years ago but never went to Sierra Nevada but heard from other instructors, OK for beginners better for intermediates but limited for expert skier/boarder due to lack of hard black runs.
Avoid weekends and Spanish holidays as it can get very busy with locals, weekdays are much quieter.
Its definitely something I will be doing, well worth a few hours drive.
Richard