I think a must is llama, or tasker if you have the money.
You can customize your phone for almost anything automatically.
I have mine set up like this
9pm until 6:30am turn on aiplane mode and turn on wifi and it goes into silent mode(I do this because I live in the basement so I dont get reception anyways)
When I get to work, it goes back to "work mode" which sets me profile to 1 volume on everything.
When I plug my phone before I go bed it opens up the whatsapp into my gf's profile so I can text her good night( saved my life!!) haha.
Thats just a few things I can do with llama.
Another few things, I just rooted my phone yesterday so I can play playstation(Megaman and Final Fantasy) games with my PS3 controller, and so I could get jellybean. On top of the usual ROMS. ( I am not saying you should root your phone, Im just saying that what I did)
Not using any case, its a big phone already, I dont want to make it bulkier specially since Im considering buying an extended battery.
I also switch from a 4S a last month and after many hours of research( probably like 50 haha, i do research on my phone like its my job) I am very happy with it