The most recent Hyperspace Postnotes has even more details about the space battle, specifically the opening shot.
Here's a run down of the highlights:
-The article says the Confed. ships trying to escape from Coruscant. This makes sense since they have just managed the incredible feat of kidnapping the Supreme Chancellor. They no doubt wish to get away before the Republic fleet can bring enough force to bear to block their retreat. Unfortunately, a considerable number of Republic ships have already arrived and have engaged the Seperatist fleet by the film's opening.
-Obi-wan and Anakin's main goal in the battle is to reach the Seperatist cruiser which is holding Palpatine and rescue him, not to engage the enemy fleet and it's fighters.
-Anakin and Obi-wan will fly their fighters in a synchronized fashion, matching each others movements in space perfectly. This is supposed to be a way to show how great a team they are, and to make their inevitable split all the more gut-wrenching.
-There was an idea to have the battle taking place so close to Coruscant that ships and fighters were interacting with some sort of planetary radiation shield or some other type of field above the planet. This would have been used as an excuse to show energy bolts with a trail effect like real life machine guns. The fighters' engines would produce a ripple effect behind them as well. Thankfully this idea has so far been left out of the shots.
- The Republic ship model we discussed recently is probably going to be in the film. The Postnotes has pictures of early animatics of the battle and the Venator class(which the model most likely is) shows up several times.
-A Trade Fed. battleship appears in one of the pictures with the Venators and my guess now is that the Venator is much larger than an ISD, and is most likely some sort of cruiser, or battlecrusier. But this is just speculation based on animatic which may change.
-There is a picture that provides a fairly close shot the Venator's guns. It has 4 large turrets on each side of the dorsal hull. The barrels are clearly visible. Unfortunately, the shot is at angle that makes it hard to determine the exact number of barrels. However, the guns do look dissimilar to the ones on the Acclamator class.
-It seems that the Republic and the Separatists are fond of hull paint schemes. One of the Trade Fed. battleships had one in green and all the Republic ships have a Red and gold one that resembles the kind of paint schemes on the Republic gunship along with other Republic ground vehicles.
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More details about the battle also showed up in the latest homing beacon. Here is a list of ideas that were thrown around for so-called "mini-dramas" which play out during the battle. These ideas may or may not show up in the film but do give us an idea of the direction the VFX guys are going.
-Colliding / scraping starships
-Sacrifice ship to break through blockade
-Diving formation of assault frigates to save cruiser from swarm
-Shockwave causing havoc from large explosion of ship
-Shockwave bombs across surface of larger ship causing damage
-Shockwave bomb on droid fighters
-Tractor beams picking up ships to repair / collision
-Pockets of intense debris caused by explosion that heroes fly through
-Reinforcements dropping out of hyperspace to help less-than-fortunate ship
-Launching and docking tri-fighters / clone fighters
-EMP bomb causing loss of power to large ships, out-of-control collision
-Vulture droids landing on large ships and attacking
-Leaking fuel ignited by ship passing
-Combined ray attack
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My only complaint so far is that this Venator class is the only type of Republic ship mentioned or seen so far. I had personally hoped to see a Executor-like, death-dealing, KDY monstronsity appear to educate the Seperatists about the New Order.

I can only hope Lucasfilm simply wishes not reveal all of the ships that will appear in the battle.