Good write-up!
Couple of questions -
Does this switch require any modification to the existing, or replacement of, the Battery Tray?
Do you need to install longer Battery Cables as with some other type of Batteries?
Did you happen to ask them if there are any charging issues for these batteries with the standard 120-Amp Bosch Alternator?
I ask because some Deep Cycle AGM batteries can overwork an alternator, sometimes leading to early alternator failure. Also, what is the optimum charging voltage? The Bosch is generally around 14.5 volts (though you can alter this with an internal voltage regulator swap), but some batteries prefer more/less voltage (true Gel batteries prefer much less).