I started off back in 92 or so with Devpac 3, and I loved it. Then I switched to AsmPro when I came back to Amiga in 2001. I still much prefer Devpac and only really used AsmPro due to my inability to get a hold of Devpac 3 disks back in the day. AsmPro is fine, nothing against it, I just found Devpac's editor much better, and more professional.
