The extended events seem like a better technology and less stress on the server, but the SQL Profiler/perfmon has better tooling. Also the extended events seem to have a steeper learning curve. In which context should each be used? Is it worth getting past the steep learning curve to take advantage of the extended events?
Definitely yes. Extended Events is a new platform with better performance, scalability than SQL Trace and the functionality that is in SQL Server 2008 is kind of limited when compared to SQL Trace and also there is some learning curve. Rest assured, Extended Events is getting a major over haul in SQL Server DENALI and there will be lot of options & use cases available in Extended Events that won't be in SQL Trace. Extended Events is the future of monitoring & troubleshooting going forward and some day in the future SQL Trace will be removed.
Note that MSFT won't deprecate a feature right away when a new platform is introduced. Extended Events is in Version 1 (SQL Server 2008) and there are lot of things that need to be improved, modified before removing SQL Trace which was there in the product for a long time.
To get over the learning curve, practice examples from blog posts written by Jonathan Kehayias and few of mine too (shameless plug).
To Sandy: a I don't think Michael has asked too many different questions on various topics in this thread. Yes there are many questions but they are on the same topic. I don't think he should open up several threads to split this one.
SQL Server traces and Profiler can be used for auditing, but as the feature is announced to be deprecated in future versions of SQL Server, it’s not recommended to use this approach moving forward.