Just bought a 54" one myself. I have only cut with it once so I really dont have any good pro/con for or against the 810. I paid $7k OTD with mandatory SC taxes.
Only thing I can say is that it seems that if there is a con, that the con is a generalization of all ZTRs. For example, it is a little bumpy on not perfectly smooth ground(even a suspension seat will not help with a stiff, solid frame). If your turf is not really well established, the zero turn part of the name really isnt possible because it will "tear" into the grass on quick "zero" turns(not too bad if you keep both wheels moving without any one wheel turning in place). It's easy to ring out the grass around a tree(no real fix for that). If you have never drove a ZTR, you lose any and all reference for driving straight because you no longer have a tractor hood to look down. Also, when its dry and dusty, you really get in the middle of the dust cloud, especially when making a turn. A dust mask will definitely be worn next time.
On the upside, man this thing cuts like crazy!! Wide open, even bahia grass. Motor never bogged down even in high grass. All of it was down clean at the 1.5" deck heght setting. At 2.5" deck height, it stringed a few of them. Looked like I laid carpet down behind me.
I love mine so far anyway.
Rod