I dont know anything about Compak grinders, but I recently upgraded from a doserless Sunbeam 0480 to a dosered Mazzer mini.
Quite a noticeable improvement in taste...but I dont like the doser. I thought it would grow on me, but its more a hindrance than help.
If the Mazzer just dosed straight into the PF it would be perfect for me.
Others here who have upgraded from doserless to dosered love it though.
I really depends on what You want.
Youll get opinions for, and against dosers, but its you that needs to live with it in the end. :)