It seems some people are determined to take this as bad news. There are a lot of reasons why this is a good thing.
-Offloading the cost of marketing, packaging, and shipping to Paradox gives Obsidian more capital to invest into the actual game. Now they can bring more developers on and create new content or just polish the existing content to a higher degree than they could have afforded to before.
-Obsidian is still doing QA, they're just doing so in conjunction with Paradox. We don't even know how patches will be distributed yet (through Obsidian or Paradox) so it's kind of pointless to worry about QA on those at this point.
-Marketing might not be a big concern for those of us who already invested in the project, but every copy of this game that sells through retail, digital distribution, or whatever is more money in Obsidian's pocket to put into their next kickstarter project. If PoE is really successful, other major developers might try doing kickstarter projects as well.
-Say Paradox tells Obsidian they don't like the game and it's not up to snuff. First of all, if the game really isn't very good, is that a bad thing? Just because it's a publisher saying that doesn't mean they have to be wrong. Second of all, Obsidian can always tell Paradox to go fuck themselves and just release the game on their own. I seriously doubt the contract doesn't include an escape clause for Obsidian. I also seriously doubt Obsidian would have given up any creative control when entering this deal.
So, again, Obsidian gets more money to spend on the game itself and Paradox gets a share of profits off of each copy sold at very little risk to themselves. Obsidian gets extra assistance with QA and doesn't have to pay for marketing, nor to send out backer rewards. Where was the downside?