You can avoid surface not waking from sleep by doing the following:
If it's charging when it goes to sleep, make sure it's also charging when it comes out from sleep
If it's not charging when it goes to sleep, make sure it's also not charging when it comes out from sleep
It sounds crazy but it works. I submitted it to WindowsCentral as a news tip but they don't seem interested.
Also - if the issue does occur, try shutting the keyboard and reopening. Then press power again. Or try connecting/disconnecting the power lead and pressing power again. It's much better not to hard reboot if possible, as this often results in corruption on the disk.