I am far from being an expert on this GPSS steering thing.  But I do know that my TruTrak with GPSS will fly the signals from my CNX80/GNS480 including procedure turns and holding patterns with perfect entries.  You enter the hold just like you would enter a "direct to" waypoint, but you hit the hold button instead and you get a screen that asks inbound course, turn direction, leg length, etc.  It draws the hold on the map screen and it flies right into the hold.  No wind correction, no timing, nothing.  It's like a 777!

 

You're right about the turn anticipation, but it's really a lot more than that.

 

Mike Easley