Details are sketchy, so I don't want to send out too many alarms yet, but Thomas Richard reports numerous problems after installing the new ATM 4 Deluxe. He claims that Conflict Catcher confirmed that ATM was the source of crashes involving ClarisWorks and Freehand, just to name two. He further reports that the earlier version of ATM 4 that shipped with Acrobat 3.0 does not show these conflicts.
In contrast, Eric Belsley (on the MRP today) has some positive words about the new ATM Deluxe.
In any event: if you install ATM 4 Deluxe, note that it deletes any previous version of ATM that is on your disk. So make sure you have a back up copy of your older version handy, just in case you want o downgrade back to it.