I hate to burden all of you with two news updates in a single morning, but this news tidbit was too juicy to ignore.
1up.com has released a final preview of Final Fantasy IV Advance, detailing the new dungeons and returning characters. I'll cover their preview to the best of my ability, saving you all the trouble of reading the 1up article yourselves.
To refresh your memory, FF IV Advance provides improved graphical textures, new menu portraits, and a refined translation compared to any previous version of the game, plus adds two new optional dungeons and a means for replacing characters in and out of your party. The game's difficulty is the same as it was in the original Japanese "Hardtype." For better or for worse, several spell names have changed, using the ara and aga suffixes rather than the oldschool numerals and changing Meteo to Meteor (I personally find that last edit disgraceful).
After defeating the Giant of Babil, you can replace Kain, Rosa, Rydia, or Edge with Palom, Porom, Cid, Edward, or Yang, each of whom was in your party sometime earlier in the story. Each of the five returning characters have had adjusted stats to make them useful in the new lategame. Cid "is a total hoss", featuring superior HP and Defense compared to other characters and Edward, while as frail as ever, is adept at inflicting status effects with his harps (far more so now than on the SNES). After re-recruiting these five characters, your party can return to Mount Ordeals for a short but intense 8-floor dungeon whose end features five new powerful weapons, one for each of your returning characters. Yang's weapon is the holy-elemental Hand of the Gods, Cid's is the randomly-Thundaga-casting Thor's Hammer, Edward's is called Apollo's Harp, Palom's the Triton's Dagger, and Porom's the Seraphim Mace.
If that wasn't enough for you, there is still another optional endgame dungeon, The Lunar Ruins found on the Moon. Once you've beaten the game, this new dungeon is unlocked, featuring nine special sealed gates, one corresponding to each character, with Palom and Porom sharing the same gate. In each gate, you'll first need to endure a brutal dungeon that makes the Path to the Core "look like a cakewalk." The early levels of the Lunar Ruins feature monsters that we're already familliar with, like Behemoths, Minds, and Wicked Faces from the final dungeon, but the lower levels include new monsters that are more difficult than any random encounter in the game. At the end of each of the sealed gate dungeons, you'll need to take the associated character along for a special trial - these trials range from Yang taking on dozens of powerful Monks to an airship-flying minigame for Cid. At the end of each set of trials we fight a beefed-up Lunar version of one of Rydia's summons, with HP ranging from 90,000 to more than 120,000. Beating each Lunar Summon will net you a new powerful piece of equipment and a special item called a Grimoire. Getting all nine Grimoires will unlock the game's ultimate challenge - "an unbelievably difficult fight that should make aficionados of FFIV trivia particularly happy."
So that's the game. This seems to be very similar and at the same time very different from the Dawn of Souls remake - there are a great deal of new features but instead of dumbing down the gameplay experience, it's more hardcore than ever. All of the information I've provided is derived from Gamespot's screenshots archive and 1up's detailed preview linked in the first paragraph. Final Fantasy IV Advance is released December 12th, 2005 in the US.