The battle system is... pretty interesting. It's almost like a miniature SRPG, though the arenas are quite small so you the fights don't take anywhere near as long as those in an SRPG (though you don't have as much depth, either).
Easier to describe with a screenshot:
The bar down the left is the turn order, much like in FFX's battle system. When it's your turn you can use regular attacks, items, move (you can move as part of the attack/craft commands or just move on its own), etc. Some turn slots have bonuses attached to them (which you can see to the right of some of the character portraits). If your turn has one of those attached you get that bonus - be it increased damage, EP (MP) recovery, CP recovery (Craft Points, regenerates when you attack/defend and is used for special attacks), increased chance of an item drop, more sepith (explain this in a minute), etc. Of course, the enemies get the bonuses too, which is where S-Crafts come in. These are your real... I guess I'll just call them limit breaks. You can use these at any time providing you have more than 100 CP, and when you activate them that character will be automatically inserted into the turn order after the current attacker. Which is awesome if you want to either use a healing S-Craft in a pinch, or make sure that you get a Critical turn bonus (or even use an S-Craft you didn't really want to use simply to avoid an enemy getting the critical).
They're... well, average in terms of pacing I guess. Usually you can reach the enemy on the battlefield in a turn or less, so they're not really
that time consuming, although some enemies can be a little annoying. The difficulty level isn't that high really, some enemies can be annoying and give you a tough fight, but I don't get game overs very often (and if you do you get a 'retry' option that just puts you back to the start of the fight, no progress lost).
There's a whole lot of optional sidequests though. In Sora FC/SC you play as a group of Bracers, who basically travel around dropping into the local Bracer Guilds, where people can leave requests to hire your services to do stuff for them in exchange for money and quite often other rewards too. You only really have to do the bare minimum of these, but there's a whole lot of them, most of which appear on the notice boards in the Guild for you to check with details of the client and money rewards, but some are hidden. Doing them gets you money and BP (Bracer Points), and when you get a set amount of BP it increases your rank and gets you a (usually useful and rare) reward from the Guild. Some of them have other optional objectives or choices which determine whether you get any bonus BP or extra rewards, too, and if you get all the BP in FC or SC you get a bonus at the start of the next game. In addition to that there's hunting for volumes of a novel (get them all for Estelle or Joshua's ultimate weapon) and collecting issues of the local newspaper every chapter. The novels actually turn out to be surprisingly connected to the story, too, and the great thing about the quests is while there are lots of typical RPG style fetch quests or whatever, quite often it's worth doing them just to see the character banter. Rather than simply walking up to someone and them saying 'get me this', there's always a conversation before and after, and some of them reveal some interesting things about the world, while others are just funny.
The other gameplay system worth mentioning would be the Orbment system. This is probably easier to explain with a picture too I guess.
Every character has an Orbment similar to the one on the right. Every character's is different in design and how the lines are ordered though - more magic (Orbal Arts) oriented characters generally have less (or only one) lines than characters that are primarily fighters, who usually have loads. In each of the Orbment 'slots' you can set a 'quartz' which has a set effect (Attack up by X%, Defence up by X%, HP recovery in battle, monsters ignore you on the field, etc etc). Some characters have slots in which you can only set a certain element of Quartz. Anyway, each Quartz has some set elemental values (see the numbers under 'Line' in the top right), and these decide what Orbal Arts that character can use, like a low level healing spell may need 6 blue, or whatever. This is where the lines have an effect, because the numbers are added up for each line, so if you have 4 blue in line 1 and 2 blue in line 2, while that may add up to 6 that doesn't get you that low level healing spell. The middle quartz is added to the values for all lines.
Anyway, you can get the quartz in a number of ways - either dropped from monsters (very rarely), through quests occasionally, or, more often, by exchanging coloured fragments called Sepith that are dropped by monsters at the town workshop. Or, alternatively, you can exchange the Sepith for money there - monsters don't drop money, so you get it by selling items, doing Bracer quests, or exchanging Sepith. Usually you'll want to get Quartz with them though. The whole Orbment system is
very important to the story.
As for the split between doing various things, depends how many Bracer quests you do really. If you don't do many at all then perhaps you could push it to 70/30 in favour of dungeons, but if you do them all you're easily going to spend more time around the town than you are in dungeons and fighting. Falcom always puts the games down on their IR reports under the genre 'Story RPG' and it shows.
Okay I think that'll do for now.