Got my Samsung galaxy S4 yesterday and have given it a run. The one underrated app is the watchon app. Basically, it's a remote control app which also makes suggestions for programs to watch based on your preferences. You can also watch these within the app as well. The remote control has worked brilliantly on my lounge and bedroom tvs and the sky+ box, as well as my Hitachi freeview box. You can also allocate and name different remotes to different rooms.
So far the battery life is better than on the galaxy S3 with most futures on. Just I've 24 hours.