jedi45612 posts a few EP3 quotables from Rick McCallum in the latest SW Insider. From the EP3 spoiler forum:

McCallum said that Ep. III "in terms of scale, in terms of what's going on, in terms of story, everything it's going to be the biggest one.".... He also said there would be spectacular and numerous lightsaber battles. "Episode III is the last one. SO no-holds barred now." He also confirmed that Nick Gillard is coming back. And he wouldn't promise a happy ending. "There's not a lot of light there."

Update: More production news from Rick in the Star Wars Insider:

When Star Wars Insider asks producer Rick McCallum for an update on Episode III, the first thing he does is offer up a laundry list of what's about to happen:

"I finalize the deal at FOX Studios, Sydney in about a week's time; I've got our production designer starting in October; Our costume designer starts next month, and she starts shopping for fabrics. We're equipping the sound stages, sending in stuff from England back over to Sydney. So we're in real "go" mode now."

Until then, most of the pre-production work remains in the talented hands of JAK Productions, whose members meet with McCallum and George Lucas each week to show concept designs.

McCallum laughs as he explains the discrepancy in desired screenplay by adding, "George says he's writing, so we're just moving forward, trying to make him feel as guilty as possible." The possibility that george Lucas will employ a co-writer for Episode III remains "impossible to tell" at this point, but McCallum expects the screenplay will be finished next spring.

Location Scouting
McCallum hasn't started location scouting for Episode III. "I'll probably start doing that when [production designer] Gavin Bocquet starts, which will be in late October."

Lightsaber Training
He demurs when asked how Lucas and stunt coordinator Nick Gillard could possibly top the Jedi fight scenes in Attack of the Clones, but reminds us, "Episode III is the last one, so no-holds barred now."

The Fall of the Republic
In addition to being the last Star Wars movie, Episode III also promises to be the darkest chapter in the Skywalker saga. "I can't promise a happy ending," says McCallum.

American audiences are notoriously unwilling to accept movies with a downbeat conclusion, but McCallum is not worried about how fans will approach the saga's most ominous episode. "I think we'll be given a lot of leeway there, because most people understand that this is just a chapter. Yes, the film has to work within its own context and work as a film complete unto itself, but when we're talking about the issues that we have to deal with, there's a lot of light there. Most people who know the Star Wars saga know that this is Anakin's destiny. In many ways, he is the Chosen One. Without him, the galaxy would never be saved."

From that "certain point of view", there will be at least a glimmer of light at the end of Episode III, since we all know where Anakin's journey ultimately leads.

Despite these general predictions, McCallum remains carefully coy when asked whether fans should brace themselves for the deaths of important characters. "You should definitely brace yourself for that." he laughs, refusing to give any more specific hints.

You can read the full report in the Star Wars Insider available at bookstores and larger newsstands. Thanks to Grilled Sarlacc for the scoop.