Have gone skiing many times at Northstar as it is one of my favorite resorts in Tahoe. The resort has gained a lot of popularity in recent years so I would recommend getting there early in the morning. Otherwise you end up parking at the top of the parking lot and it takes you a half hour to get on the hill with lift ticket lines.
The resort has improved with Lookout Mountain which offers terrain for more advanced skiers. The backside is awesome - it offers groomed runs, some tree skiing, powder, and moguls. Runs are long and steep, however the lift line at the bottom can be 15-20 minutes on busy days.
The frontside isn't too bad. I usually start over on Vista and ski a few runs over there to warm up. Comstock can be a really busy lift , although it services several runs. Overall, this resort is above average for Tahoe.