General

A new Pokemon anime short came out just for Omega Ruby/Alpha Sapphire, similar to the one that came out for Black 2/White 2. Currently in Japanese only though.

Video here:

As the game is out now for most of the world, much more info is becoming available, though I'll try and avoid story/etc spoilers if I can. Version exclusives have been updated from what we previously knew.

serebii.net/omegarubyalphasapphire/exclusives.shtml
Omega Ruby: Seedot/Nuzleaf/Shiftry, Mawile, Zangoose, Solrock, Groudon, Palkia, Throh, Tornadus, Reshiram, Skrelp/Dragalge, Ho-Oh, Latios?
New!: Kabuto/Kabutops, Shieldon/Bastiodon and Archen/Archeops fossils are exclusive to this version, but can be traded over.
New!: West Sea (Pink/Brown) Shellos/Gastrodon is exclusive to this version.

Alpha Sapphire: Lotad/Lombre/Ludicolo, Sableye, Seviper, Lunatone, Kyogre, Dialga, Sawk, Thundurus, Zekrom, Clauncher/Clawitzer, Lugia, Latias?
New!: Omanyte/Omastar, Cranidos/Rampardos and Tirtouga/Carracosta fossils are exclusive to this version, but can be traded over.
New!: East Sea (Blue/Green) Shellos/Gastrodon is exclusive to this version.

You definitely get given a Latios or Latias depending on your chosen version, though it's not known fully yet if the other one is in the same game.

Also apparently Surfing seems faster and the encounter rate while Surfing seems much lower.

Using the DexNav, as far as I can tell, any random encounter Pokemon can be found with it's Hidden Ability.

You can get the other lati@s not in your game by getting the Eon Ticket, which can be received by streetpassing someone with the Eon Ticket.

Also, don't forget to hop onto Mystery Gift and get a Shiny Beldum with it's mega stone.

Also if you haven't already, get an ORAS demo code so you can get Mega Glalie (Or mega Steelix if you're in Japan)

Are both games split up between who you're fighting, or does it follow more of the Emerald storyline where you fight both at the same time?

I never really played Ruby or Sapphire, all of my experience was with Emerald, so, I'm kinda torn on which game to get.

They follow the Ruby/Sapphire split storyline, not the Emerald connected one, though there is an extra 'Delta Episode' that is the same for both games after you beat the main storyline.

You'll be fighting against Team Magma in Omega Ruby while Team Aqua will be friendly, and in Alpha Sapphire you'll be fighting against Team Aqua while Team Magma will be friendly.

West Sea (Pink/Brown) Shellos/Gastrodon is exclusive to Omega Ruby, and East Sea (Blue/Green) Shellos/Gastrodon is exclusive to Alpha Sapphire.

Also the DexNav will allow you to find wild Pokemon with egg moves - beware as some of them may hit you really hard at early levels.

More Pokemon have their own Surf sprites too. Kyogre moves a little faster than normal, and Sharpedo moves twice as fast, interestingly.

Edit: For those who like the Lucky Egg item which boosts experience gain, you can find it by using the DexNav on wild Pelipper's.

I finished Alpha Sapphire in three days like I did with X and Y, already been through the Delta Episode and started hunting down the legendaries. Already have Cobalion, Cresselia, Rayquaza, and Mesprit. Have yet to find Zekrom, Reshiram, Giratina, and Kyurem soaring on Latios over Hoenn...I also have to go back and re-capture Primal Kyogre and Deoxys, I killed them both the first time.

I liked the Delta episode, it set down some interesting things for a bridge game like say Pokemon Z or Delta Emerald to span both Kalos and Hoenn with the Battle Frontier as the connector. A lot of hints were dropped at the Battle Resort that there WILL be a Battle Frontier created for the next set of games just like in the original Emerald where it was first introduced. I never got to see it in the original Emerald, I COULD NOT beat the Pokemon League.

Preview video of a new legendary Pokemon, Hoopa, a Psychic/Ghost type. Seems to be based off a djinn (some may know these as genies):

Apparently Hoopa will be the event Pokemon release for the 2015 XY movie in July this year, hints were dropped in trailers about it and we see the same rings that are in ORAS for the legendaries on the Mirage spots. Unfortunately since I have to be part of the North American event release we won't get it until 2016 after they've CG'd the hell out of the movie and dubbed it for us stoopid North Americans who don't want to make the effort to read subs.

Funnily enough, Gen VI is the only one so far that doesn't have a legendary trio (like Articuno/Zapdos/Moltres) at all. It's interesting.