I found that sims didn't help private pilots as much as they hurt. It did help on navagation, but they wouldn't look outside, and their plane handling was poor. There were a few exceptions, I had one guy who had never flew a real plane before, and he was holding altitudes, looking outside, everything. He was flying like a 30 hour pilot. I can't say the same for most in his position, though.

During instrument training, however, sim time is priceless.