At work we leave them on always, some of them with hybrid sleep, some without sleep; and home, I leave a couple of PC's on (with hybrid sleep enabled) all of the time. I have no problems. They get reboots when updates require it, but not much more than that.
At work we do this because there are some machines that run equipment, so they are on always; and our desktop machines we leave on always so that virus scans and backups can happen daily at night. I've done it that way on probably about 300 computers over the past 10 years.
At home I do it because it is so fast to wake the machine up compared to booting when I want to use it, and energy consumption during hybrid sleep is about the same as the computer turned off. I wiggle the mouse or press a key, and the machine is awake and ready to go in about 4 seconds. From an asleep machine to first web page up and viewable is typically about 8 seconds, and a couple seconds of that is me typing in my password.