I've done some X10 in the past, but now all my stuff is Insteon (and most dual-band, which actually works quite reliably). I have a few things installed in my house now, which while they are part of an "automation system" I'm not sure I'd call it a "smart home":
* Keypad by the front door
* Has a button that both shows if the garage door is opened/closed and can open/close it
* Has an 'all off' that turns off the kitchen / living room lights
* Can control the outside soffit plug for x-mas lights
* Outside lights
* Turn on to 50% when it gets dark (ISY99 controller that automatically accounts for DST changing of daytime throughout the year), turn off at midnight
* Quickly go to 100% when there's motion outside, OR if the garage door is open, anytime when it's dark out
* All transitions fade: eg, After motion stops, they take ~1min to slowly fade from 100% back to 50%. This is subtle and just a nice touch that's easy because of the system
* Kitchen keypad has 'bright', 'dim', and 'off' buttons, which control the lights over the island, sink, range hood and under-cabinet.
* There's also a button used to indicate if the garage door is open, so we can see from the back half of the house
I haven't installed it yet (change of season made it not important now) but I will be adding a keypad to the bedroom to control the fan/lights. Right now there's just one switch and if you want fan/lights you have to pull the chains. During the summer we are constantly walking into the dark room, turning the switch, and all that happens is the fan turns on.
I think for me, a lot of the use case behind using insteon, is less about 'automation' and more about being able to make virtual 3/4/5-way switches and scene-based lighting without having to rip apart drywall and rewire.
Heck, one really convenient thing is that the switch in the living room controls lights on the other side of the room -- without a plug-in module, I'd either have to adjust those lights manually (meaning they'd be left off and/or on all the time), have an extension cord running in front of my fireplace, or open up drywall to rewire. I didn't build the house or choose to make the switch operate a plug on the same wall 6ft away, but at least I can make our lives easier with very little effort.
A lot of this is really just laziness in way, but at the same time, when you have to use 4 different controls in the kitchen to get all the lights on/off you simply don't turn them on and/or leave them on most of the time. One button gets better use of what's there, and just makes life a tiny bit more pleasant.
One thing I really don't get is the fascination with using smartphones to control. I've tried it, I just don't find it useful or convenient. Assuming I have my phone on me (I don't always, while at home), I have to take it out, swipe to unlock, wait a second for it to load, find the control app, wait a second for it to load, find the lights/scene I want, then change it. How the hell is that more convenient than the switch/keypad that's always on the wall right next to the door that I walk by as I am coming into the room? Seriously, I don't understand.
This whole 'you can control the lights from anywhere' thing is just a non-existent use case, as far as I'm concerned. We accidentally leave the lights on maybe a handful of times a year.. that is not a primary case of why to install these types of systems. I haven't even had my system exposed to the internet for the last couple years (changed my router, and never set up port forwarding again) because I NEVER used it remotely.
I have a wifi-connected thermostat, which is great for exactly 3 reasons: It is miles easier to program than the cheap piece of crap it replaced; I have a linux cron job that turns on the fan a few times through the day that greatly helps balance out the temperature (otherwise the back of the house facing the sun gets significantly warmer than the front), and I could only find this feature on MUCH more expensive thermostats; and lastly, I can adjust the temperature from my bed, particularly handy on holidays when we're sleeping in but the temperature is set as if we're away at work.