Take note that this is an in-store special so it is unlikely that you'll be able to order the HD-A2 through Walmart's website at this price. Also, this price is not valid in Wisconsin, Oklahoma or Utah as it is illegal to sell items for less than cost in these states. According to the manager at my local Walmart, those that live in these states will be able to pick the player up for about $198.
Needless to say, there will probably be a mob of people outside of your local Walmart tomorrow morning. Be prepared to get there early and wait in line.
Update - Best Buy has also lowered the price of the HD-A2 down to $99.99. There doesn't appear to be a limitation for those, like myself, that live in Wisconsin either.