The nice thing is it's no longer a 1 percenter'ish thing to have anymore. Most of the the things on ours are free (skype, lists, calendars, weather, etc...). Music is cheap (a $20 bluetooth receiver attached to an existing sound system + free Google Music cloud storage + Spotify, Pandora, etc...). The TV/video stuff is cheap too ($90 Nexus Player acts as a chromecast and runs XBMC, Netflix, Hulu, etc... can also run emulators). So it's maybe $120 to get a ton of functionality out of an old tablet.
The home automation stuff is the most expensive and it's certainly not necessary: sprinkler controller ($100 - $150), heating cooling ($100 - $250), lighting control ($40 / switch or $15 / bulb), security cams ($250 for an HD 4 pack), and the controller runs on a raspberry pi with a zwave dongle. So there's maybe $700 - $800 tied up there.
It's easy to pick up another galaxy tab (7" for $90, or 10" for $130) and clone all the functionality to it when we want a controller in another room. Plus all of that can be copied to your phone as well. iPads would work too, but you'd lose all the convenience of the widgets and the built - in IR blaster.