Colluding miners attack: Is the Bitcoin protocol compromised?
The report is not heavily disputed.

In the hours following the paper's release, several developers are discussing solutions:


http://www.mail-archive.com/bitcoin-development@lists.sourceforge.net/msg03128.html


and 


http://bitcointalk.org/index.php?topic=324413.0


There has not been any evidence that such an attack is imminent or likely even.  And remember, even an attacker with 51% cannot do much.  One risk is that a transaction could be canceled after it has confirmations, if the selfish pool is that much further ahead.