If I were to design a house I would design it around two rooms - the kitchen and the bathroom. No matter what else happens, you have to eat and you have to potty. Sure you have to sleep too, but I have been know to do that in either of those rooms! (those are other stories for another day)I don't think nearly enough people invest enough time or energy thinking about their bathroom. It is probably the most personal, private, intimate room of the house. Unless you have small children, the goings-on behind closed doors are rarely documented. It's just a personal space.
Because it is so personal, I don't feel like I can really comment on what is "necessary" in a good bathroom for anyone buy myself. Even my husband and I have different ideas about what is essential and what is optional.
The only universal essential in my mind (aside from the obvious hardware) is comfort! You want to enjoy your time in your bathroom. Our master bathroom is ultimately what sold the house to me, although the kitchen was a very close second. The bottom line was that I knew I would enjoy this bathroom. We put more hard work in this room than any other. And this will continue to be a work in progress for both of us.
The thing I love most about the bathroom is obviously the great big tub. The hot water heater isn't QUITE large enough to fill it all the way up with super-hot water (which I know is probably not super healthy anyway, but I love it!) but it is still lovely for soaking. There is more than enough room for all of our stuff without feeling like it's crammed everywhere. There is still room to turn around. And if Jeff and I need to get in there at the same time, we can.
The thing I hate is that it's really cold. It's on the corner of the house. It kind of sticks out and isn't very well insulated. The floor is ceramic tile and it has two big single-pane windows. It doesn't matter what you do, it stays very very cold. We put in a small space heater which only helps a tiny bit. We're working on it.
My biggest word of advice when it comes to outfitting your bathroom is don't skimp on quality. Sure, know your budget. But maintain high standards! Choose a color your enjoy, you'll be staring at it a while. Buy good towels. Even if it means you buy fewer and wash them more often, it's worth it (and if they're quality, they'll hold up to the washing!) Make it a place you enjoy!