Ordinary people still have no reason to use bitcoins (rather than old money) to buy things on retailers like Overstock. So that option should not bring more old money (USD etc) to the Bitcoin market.
Speculators and miners who want to leave the Bitcoin game now have the option to cash out in merchandise (at a few merchants) rather than in old money. That only makes it a bit easier for them to decide to leave, and hence take old money out of the market.
So the Overstock news is "good news" only for True Believers, who did not need it to believe anyway...
A big brand using Bitcoin is good for marketing. More people will hear about it. So this should bring more "old money" to the bitcoin market.
Right. How someone could say that Overstock taking bitcoin payments is bad news is incomprehensible. It just goes to show you the Catch-22 many bitcoiners have rolling around in their brains.