Nice technology, however one will have to consider several things and specifically the impact on temdb carefully.
For understanding SQL Server locking, Erland Sommarskog has a great script: Download now, that you can use to see locking behaviour on SQL Server.
MSDN article "SQL Server 2005 Row Versioning-based Transaction Isolation" by Kimberly Tripp and Neal Graves is a very comprehensive treatise :w00t: on the subject of row based versioning. In there the different cases under which certain isolation levels are to be considered are discussed with pros and cons.
In my opinion, deciding on an isolation level in 2005 or 2008, you have to know your application's needs very well and also be very up to scratch on how you configure your SQL Server disk array, especially if you operate on a SAN, particularly where to place tempdb. Make a mistake with one of these and your Row versioning based transaction isolation will be an impediment rather than salvation.:hehe: