I never really saw a need for it, but if you want to use it you can. It just isn't really necessary for, in my opinion, a general hobbiest's needs. Now if i had a store I was running or I took care of sick reptiles often, then I could see it being more useful. Just depends on what you need it for. Although I guess it could come in handy if you had a sick dragon.
And the dilution you would use depends on what you want it for.
The products website says this:
General disinfection at 1:500
High level disinfection against bacteria, fungi and most viruses at 1:250
For use against the most resistant viruses such as Parvovirus or PBFD at 1:125
-Brandon