Curious about people's opinions here. I have a guest room with full bath detached from the main house. It's only ever used occasionally, generally by family when they come to visit. Part of me wants to outfit it with switches and sensors to work like the rest of my house, but then part of me realizes the people that stay in there could probably care less about it.
Should I do it or leave it alone?
Do it, but add the extra option of being able to disable all the Rules with one virtual switch.
The problem of course is not knowing what "they'd" like. Me, I'd focus on turning things OFF. That's the only portion that would help me, the electricity payer.
Don't do the light switches. Guests hate -and vocal about- the change on-off action of paddle-style switches.
I agree with @csteele - do it but have a guest mode - maybe a global variable (or virtual switch) that when activated prevents automated lights etc. Otherwise certain things are still useful maybe motion lighting in the bathroom, fan on in high humidity. Various lights left on alerts etc. Also good for vacation - have lights on a schedule for certain things.
best way is to live in that room for a week and get the automations all setup. I was quarantined with covid for a week last year and now I think I have all the automations in my guest room hammered out. They behave as expected and are overridden intuitively (like by turning off the lights with a pico on the nightstand).
I find there is usually something that I miss the first time I automate something and I don’t really notice until unexpected things happen. My wife tolerates it, but I don’t want that to happen to people who aren’t expecting it.
Personally, I wouldn’t use my time, energy or money automating a guest house if most of the guests couldn’t care less.
That pretty much describes my home. 160+ smart devices and only one of us cares even a little... me. No one complains about the automation, no one seems to be wishing it went away, just that no one finds it amazing like I do. And therefore, if it were me, I'd add smarts to the guest room. Just Because. Too cool not to. 
But also there is the security aspect - maybe nice to show some activity every once in a while especially if the guest room is separate from the main house. Also controlling humidity level in the bathroom is nice as well.
DUMB. 100%.
That said, most of my visitors are elderly people, and they all (universally in my case) hate smart functions. They are much more comfortable with the guest room being as DUMB as possible.
I have relatives who won't even stay all night at my house. They are intimidated by all the smart stuff. Or maybe they just don't like me. Either way it works out. I say automate and maybe you will get less company.
I go with the majority. Have anything passive (motion sensors etc) Let them turn on and off the lights manually. Leave the fan coming on automatically and if there is any sort of emergency, have lights flash but that's it...
I say leave it alone. I have rule so stop the lights coming on despite the mode. I have the motion sensor always spun to the wall when guests are here and no one can figure out a light switch - top, On, bottom, Off, hold to dim up or down. Way to much learning curve 
Just keep the water sensor under the toilet!
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