I honestly think that PDF's release date was announced after Megpoid the Music#'s just so that they could cut it off with an earlier release. I really hope that's not true, though. There's no need for the Project DIVA juggernaut to stomp all over the newcomer like that.
Like this year, they are making a "package" aroud the 9 march, this year there was project mirai (8 march 2012), the final Miku's giving day (8 & 9 march 2012) and there was Mikuflick (9 march 2012), so maybe, there will be Projectdiva F the 7 march 2013, some new concerts the 8 and 9 march 2013 and something else around Crypton's vocaloids. The release date for these two games are really close, but remember what Jack Tramiel (Atari) said : "Business Is War", Miku and Gumi are in contest. But choosing this date is not bad after all, after all these events related to Miku, the place will be free for Gumi. But yes PDF's release date was announced after Megpoid the Music#'s.
Gameplay screenshots are up. http://www.asgard-japan.com/paraphray/meg/system.html Note the three "difficulties" in the screenshots: Normal, Expert, Challenge. I assume Challenge is its own thing, rather than a difficulty.