Take this screen cap for example. If you look carefully, you'll notice a very interesting feature. Link and the Deku Babas in the foreground are crisp, clean, and bright, while the trees, mushrooms, and sun rays in the background are softer, faded, and very indefinite. This is meant to give off the vibe of an impressionist painting, and in my opinion, increases that connection to nature and makes the game seem more alive.
As far as combining Twilight Princess and Wind Waker goes, the two separate maps, Hyrule and Skyloft, reflect the respective games. Hyrule is laid out the way you expect it to be from games like TP and Ocarina of Time. But Skyloft reflects the flooded Hyrule of WW, only in the sky. But before we all get worried about more lengthy travel sequences, the developers have listened to our cries and thrown us a bone: Link's bird is way faster the the King of Red Lions. So searching for treasure on the sky islands will be fun rather than tedious. And to get between the worlds, Link skydives with a parachute that we have to control. So going back and forth is as fast as terminal velocity (since there's magical wind tunnels that throw Link up above the clouds where his bird can catch him). The maps for dungeons return, but without their faithful companion, the compass. Link's "dowsing" ability replaces that, by firing beams of light in the direction of treasure, keys, and apparently Zelda. There's also a third (!) secret world called the Silent Realm where Link learns how to be a hero by running around grabbing tears (Twilight Princess) and dodging Guardians (Phantom Hourglass) who can knock him unconscious. He gets to this "alternate world" by stabbing his sword into the ground, leaving him weaponless on the other side (which was what that stupid teaser poster was referencing the whole time).
Finally, I am super excited about the item upgrade system. A staple of all RPGs, the item upgrade has been creeping into action and adventure games at a slow rate. With this move, it seems that the Zelda crew is beckoning us to immerse ourselves more than ever into this game. Monsters drop the items used for the upgrades, and it looks like each item in Link's inventory has multiple iterations based on how you choose to upgrade it. This also opens the possibility for treasures giving exclusive upgrades, and may be a plot point, which leads to my theories from the game.
Clearly, this game's "fairy", Fi, is the Master Sword personified. She apparently lives inside the Skyward Sword, and makes beeping noises at Link when she wants to tell him something. (I don't know which is worse, beeping or "HEY! LISTEN!") I have a feeling that the upgrade system was put into place to make the upgrade from the Skyward Sword to the Master Sword make sense. This will definitely involve Fi deciding to meld with the Skyward Sword, and probably the new dowsing ability ("Dowsing" loosely translating to FIRING LASER BEAMS MADE OF CONCENTRATED SUNLIGHT! Talk about solar power.)
Secondly, while the fire temple's boss has been confirmed to be a walking rock (not like a Goron, though), the fire temple's doors have a lovely picture of an Asian dragon on them. This gives me (and a few other Zelda fans around the net) the hope that Volvagia will be in this game, and we'll get to see the Hero of the Gorons who beats her up with the Megaton Hammer.
I have to wonder what the explanation for Link's tunic will be this time. In most of the games that follow Ocarina, they explain it as dressing like (or wearing the exact same clothing of) the Hero of Time, who only dressed like that because he was initially a member of the Kokiri. As Skyward Sword predates Ocarina, perhaps this first Link is the inspiration for the Kokiri's pattern of clothing. Also, maybe OoT's Link's parents named him after this first hero, and the Hero of Time accidentally lived up to (and beyond) that name.
Finally, it seems that this may be the first game in which Link and Zelda hook up. In this game, she's not a princess, which definitely means they're retconning the "Every Zelda named after this Zelda" from the original game. But she's said to be a "a 'precious oracle' and a 'female servant of the Goddess'", which Link had no clue about, and Link only gets embroiled in the whole mess because she gets stolen by a tornado. As this picture shows, they are very good friends in Skyloft, so my theory is that by the end of the game, it gets better than that. This also means that the kingdom of Hyrule is going to get its origin story (about damn time, too), and we'll find out how Zelda becomes such a legend (you see what I did there? Okay, shut up, I know lame puns aren't that funny.).
For a great summary of what else is to come in Skyward Sword, head over to GoNintendo's summary of the recent Game Informer exclusive. The game itself comes out on November 20th for $50, but pay $20 more on the preorder and you'll score an exclusive Golden Wiimote with the Hylian Crest emblazoned on the speaker, along with a CD filled with orchestral versions of classic Zelda tunes from the 25th anniversary concert series. I haven't decided which route I'm going, mainly because the preorder ships directly to my house rather than the store, and I really want to walk into the store on the 20th dressed as Link to purchase the game.