Well, most of the time I let the game play itself, since standard attacks killed the enemy only slightly slowly than scrolling through abilities did, and the AI was reasonably good with healing. But for boss battles, I was forced to take over, because the AI suddenly became incredibly stupid and would die within about thirty seconds...
I would sometimes use abilities later in the game instead of just pressing auto battle all the time. Usually Auto battle gives you all the abilities that help kill the enemy. If you are high in the crystarium as a Synergist, usually auto battle will give you every possible buff so that you can defeat the enemy really fast. After the game, I had to do it myself.. because auto battle is not the best strategy against those tough monsters. Auto battle is just there if you want a faster battle.. but you may die through it.. so it is best not to use auto battle in a really tough fight. You need to use your abilities and plan a good strategy. In XIII the AI does everything possible for you to win.. if you have a good strategy. So I think abilities are more useful. Signature moves are really useful but you do not get them till really late in the crystarium. In boss fights.. it is more better to use abilities. In a simple battle.. auto battle helps.
♪ Cold fire clenched to my heart ♪
♪ In the blue of night ♪
♪ Torn by this pain, I paint your name in sound ♪
♪ And the girl of the dawn, with eyes of blue, and angel wings ♪
I used Auto-battle for the majority of Final Fantasy XIII. I only found a few situations in which Auto-battle is not effective. One of them is Lightning as a Ravager. Lightning's best quality in battle is her fast animations/high speed. But since she has both magics and strikes, Auto-battle will alternate between them. Using Fire, Flamestrike, Fire, Flamestrike, Fire takes a considerable amount of time longer than 5 Flamestrikes or 5 Fires, for the same damage.
Another is when I have Sazh as Commando. As most of us know, Sazh is used mostly for two reasons: getting Haste early, and his special Blitz ability. I would use Blitz almost every turn, which does not happen with Auto-battle.
A third is when I need one or two buffs or debuffs, and I don't want them in the order they give. Perhaps I would need Protect before Haste or Pain before Slow. I would use Abilities manually then.
The last is for Full ATB skills, self explanatory really.
Completed: Final Fantasy I, III, IV, V, VI, VII, X, X-2, XII, XIII. KH I, II, CoM, Re:CoM.
I use Auto-battle for quick, easy battles and when I have my paradigms set up perfectly. Every now and then I will insert a manual ability where needed, or for certain characters. Later on in the game, especially with tougher bosses, I tend to put the most important character as the leader, and manually control him/her. I find the Auto commands for Saboteurs don't work well, so I like to be able to control my Saboteur, and my Commandos.
"Escape into your own fantasies
I shall continue to dance for your world of illusions
I shall dance for eternity as the witch who brings you dread
You and I, together, we shall create the Final Fantasy..."
I heard something about it being an option where you can turn this off, but I would prefer they keep it the same like last year. Mainly because I used both manual and auto, most of the time if I know I can easily beat an enemy or im training then I auto, for the most part it really is easy to input the commands yourself, I still did it maunally (yes even on boss fights too).
Only for boss battles or hard hunts etc I would actually choose my abilities. I felt the computer knew when to use blitz before I could work it out (stupid enemies kept moving) I think it may have been even more boring for someone to actually choose their abilities then to let auto battle play. Though I would take a conscious effort to paradigm shift even if I was using auto-battle.