I use ET on my Pfaff with no tension problems. It is very linty though and I have been gradually shifting to Aurifill. I use it only for piecing, it doesn't work well for FMQ.
If you like it and it doesn't cause tension problems, use it. I was told the same thing when I went to a class on my new Pfaff. I have ignored their advice and have used what I had at home.