Well, I did see the preview at Gen Con. (By the way, I"m a "him")
It was a 25 minute preview reel, with the writer of the film as well as Charles Ryan, and someone from Hasbro that I didn't recognize her name there also to answer questions (the tone of the audience was a little dubious at first, as we all wanted it so succeed, but we know the first one sucked and hope against hope this will be at least decent). By the end, there was a general feel of cautious optimism that the movie will be fun and something we can enjoy.
Here are some facts:
It's set in the same world as the first one, as it's technically a sequel. There are references to it taking place in the same Kingdom of Ismer, and Damodar is back as a recurring villain (now an undead, and they specifically said he doesn't have any funny lipstick), it's set 100 years in the future. Otherwise, it's a completely new story with only tenuous connections to the first.
They have the 4 basic archetypes as the main characters: Cleric (including a shot of him turning undead), Wizard (including casting Lightning Bolts devastating an oncoming army), a thief (including disarming a trap they find in a dungeon), and a warrior-type (a female half-elf barbarian), they really play up her rage apparently.
Other than one actor in a supporting role, everything is new. New writers, new directors/producers, new cast. They are going out of their way to ignore many things about the first move, includng the line "Snails? Who's Snails?", delivered with a smile when the writer was asked about if Snails was ressurected in the movie.
There are passing references to other parts of D&D. The thief asks the barbarian what her kind saw in the Barrier Peaks that drove them crazy. (Yes, I know Barrier Peaks are technically in Greyhawk, but I think that was supposed to be a reference of "This is D&D")
Charles Ryan heavily reviewed the script inserting suggestions for ways to make it be more like D&D, and specifically made sure that certain D&Disms were put in, and at least mentioned in dialog to set them up for a non D&D-playing audience (we were shown a clip of a brief part where the difference between Arcane and Divine magic is explained).
When characters cast spells, they use VSM components, they didn't hammer it in with lots of explanatory dialog, but if you pay close attention, you can realize that every time any character casts X spell, they use Y verbal component.
The main villain of the movie is a dracolich (well, it's an undead dragon, and Charles Ryan said a major character is a Lich), and the cleric in one scene tries to turn him and use divine magic against him.
One character has a Ring of the Ram, and uses it heavily in a fight scene.
There are drow in the movie, but we only see their dead bodies in a dungeon.
A magmin is featured in the movie, and it specifically wasn't depicted as too bright (a reply to the answers about Beholders and other smart monsters being depicted as fairly dumb in the D&D movie, they used normal D&D creatures, and specifically paid attention to their ability scores when writing what they could do).
When the main characters enter a dungeon, all 4 enter at once as a group, and it's a big underground complex full of monsters, traps, treasure, and the like, instead of one character walking down a hallway while everybody else waits (like the first movie).
Players Handbooks were on the set/location, and the actors had to read relevant parts about their character class/race and the things they were supposed to be doing, as character research. (One way or the other, you can't say they didn't even read the PHB when making it).
It's planned for a DVD release in the USA in early to mid November, overseas it is getting a theatrical distribution in some countries (details still being worked out), and DVD in other countries. If it does well, further sequels are certain and theatrical releases are much more likely.
The only reason the movie wasn't set in an established setting, like Forgotten Realms or Dragonlance was that the movie rights to those settings were in the hands of yet another company than the D&D name itself.