I too have a 450 in my plant, only one with one expansion rack, left that is. Looking to replace it with a Do-more when funds are available. I must say though, I have never had a single problem with the 450 series, no not one. While I wouldn't trade the 250 for any other brand, I have had lots of modules fail (mostly analog and always the FACTS modules)over the years. small factor is important for me, but sometimes packing things in too tightly, I think causes problems.