I got an email asking about AutoCAD support the other day which set me thinking. I realized that I have been using Revit for as long as I used AutoCAD day to day. My journey with AutoCAD started in 1994 with R12 on DOS. I stopped seriously using it (ACAD/ADT) in 2003 and switched over to Revit. So that's nine years with AutoCAD and nine with Revit. Technically I was using Revit since 2000, but for this I am not counting the first two years since it wasn't my full time work. Some overlap existed naturally, but I've reached the "tipping point".