OK, I upgraded from the ACE 350 too. Standard mode is very similar, but not as good as Pro mode. Beware! Nickles are a high tone on the 350, a mid tone on the ATP.
Mark the connectors. Put a mark on the male end and the female end before you tighten the ring on. Make sure you tighten the ring well. It will come loose, so check it often. It will cause problems when your coil cable comes loose and you bump the cable. The marks will help you match up the ends while changing coils.
Use a coil cover, but clean it before or after each use.
You'll get much more chatter on full sensitivity. Bring it down a couple bars, except in areas with little or no trash with DEEP small targets. I keep mine down two bars unless I hit a faint target that doesn't give a vdi.
Let us know how you do. Try going back over the places you hit with the 350. I re-hunted one I found several dollars with the 350 and found another dollar or two.