David Bronman just posted a new version of the CLR Profiler that now also supports .NET Framework 4 as well as Silverlight 4. 
Key Features:

• Allows you to profile managed memory that uses .NET 2.0, 3.0, 3.5, or 4. 
  (However, you must always have .NET 4.0 installed on your box in order to use CLRProfiler V4, as CLRProfiler itself contains managed code that depends on .NET 4)
• Can target Silverlight 4 web apps.
• Can attach to and detach from live processes, to generate heap graphs. 
  (Note:  This feature requires the process to be running .NET 4.0, does not work against Silverlight, and does not allow gathering allocation call stacks.)
• Understands in-process side-by-side CLR instances, and can allow you to pick which CLR instance from a given process to profile

See more details here.