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I honestly dont know what mine is set to, but I have never had any issues with slow streaming from netflix, and have not rented anything from itunes on my ATV2....but its an interesting problem that im going to follow.
 
I have experience with this issue first hand and can confirm that reverting my DNS settings on my Airport Extreme from Google to my default ISP has led to significantly better streaming performance from Apple. I do not recall any perceivable improvement to Netflix streaming after this change.

I've noticed my iTunes purchases (primarily TV season passes) seem to download quicker as well.
 
I have a 7 mega bit connection and use Google DNS.

No problem with streaming stuff i have rented on the Apple TV.
 
OpenDNS / Google DNS

I have my home router pointing to OpenDNS. When I got my AppleTV (shortly after launch), the NetFlix app had great difficulty streaming (but not loading its catalog). I did some Google searching and found (here, I believe) that if I manually pointed my AppleTV for Google's DNS it would work, which it did. I've never had problems since then, and don't have performance problems now.
 
Zero issues with a Time Capsule configured for Google's DNS. I might try putting in Comcast's DNS entries to see if it goes any faster and grab some speedtest results, but i've had zero issues with streaming and Google. This includes: AppleTV rentals+YouTube, Netflix on Xbox360, and Amazon Unbox on Panasonic home theater box. All my devices get a static IP address issued by the Time Capsule and route through it.
 
I've got an 8 mbit connection, don't use Google DNS and my AppleTV is pretty much unusable. If it doesn't report 3 or more hours until the movie is ready, it stops and starts multiple times during the movie. Speed tests always show 7+ mbits on the download speed.
 
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