Based on a survey that I'm running on my site Poser 5 users outnumber Poser 4 users 3 to 1. When Poser 5 came out a couple of years back there were issues. Probably caused by trying to get the software out of the door too quickly. The majority of bugs were fixed in timely manner shortly after. Since then Curious Labs has continued to stand by their product and fine tune as required. I am extremely happy with the way my Poser 5 runs. I highly recommend it.