We had a hot tub at our last home. The biggest change has been our electricity bill. It is down by more than half in the winter months. If you are away, for weeks at a time, you can turn down the temp but make sure you have someone checking a couple of times a week. We had one instance that the GFI had tripped while we were away. The water was cold and we were extremely fortunate that the pipes had not frozen. If you are thinking about draining the whole unit, make sure that is an actual option.
A hot tub is really just a big tub of water. Oils on our skin affect it just like in a regular bath tub. I hated cleaning the hot tub, even tho it was only done when we changed water--about every 3 to 4 months. Any soap at all (from your skin or from a bathing suit which has not been rinsed extremely well) will cause excess foam which leads to that dreaded hot tub ring of gunge.
When deciding on decking, roof etc, remember that a hot tub creates a very damp environment and decking can become icy in winter. The roofing can hold in that moisture and may be susceptible to mold, depending on materials used.
There are many specifics for hot tub installation, including location (remember that it is h-e-a-v-y and will need to be maneuvered into position ), type of base, licensed electrician for proper hook up, to name a few.