First of all,yes,we just bought a ZD 28 to mow our "formal lawn",the reason I call the yard the formal lawn is that is the part of our property that I try to take care of,spray,fertilize,plug,ect...The rest of our land is "just grass" we also mow it,but I don't spend as much time or money on that part of the property....
Yes we have a BX with the bagger attach...We don't usually bag unless the grass has really gotten away from us,or if I have thatched the lawn and for picking up leaves...we also had a G1900S that was the trim mower,we sold it and got the ZD,with the Pro Deck...The ZD really does a super job of chewing up the clippings...we won't be using the BX for much mowing at all anymore,have clicked up a little over 500 hrs. in 2 1/2 years.
I will still put the bagger on the BX this Fall when I have dethatched the lawn...
I will tell you from experience,it takes a LONG time to get a good lawn established,our "formal lawn" is in its 6th season,and it's just now starting to really look good,deep roots, and healthy appearance.