Pat Styles explains in the windbg newsgroup the background why this managed debugging feature made it's way in public and why it has been taken way very soon.
So sad it is: likely there will be NO managed debugging support for windbg in the future. So be happy if you kept your 188.8.131.52 and make an extra backup!
As last time the highlights are very roughly described so I pasting the full list of relnotes.txt here for googles convenience ;-)
I marked the features I very personally like in green
Important changes in WinDbg 6.10:
* CE6 dump processing now works.
* NT4 no longer supported.
* Enable installation of the USB debug driver on 64bit versions of Windows.
* Install USBView.exe as part of the debugger package.
* Enable use of any 1394 cards in target machines.
* Improve 1394 debug driver reliability, responsiveness and performance.
* Improve error messages for specific 1394 driver installation failures.
* Prevent loss of 1394 debug connections after host sleep or hibernate.
* Change the 1394 debug driver to write every sent packet to the target
regardless of whether the previously sent packet was acknowleged.
* Ensure the installed 1394 debug driver is new enough to work properly with
the current release of the debugger. (Update the 1394 driver to the
version shipped in this debugger package.)
* Automatically reconnect to broken in target machines when doing 1394
* Introduce new ".dump /mA ..." option to generate user-mode minidump.
The new behaiour is the same as ".dump /ma" except that it will ignore
inacessable memory read failure and continue minidump generation,
instead of bailing out immediately. >>I've seen this behavior quite often - so thank's for that!<<
* Add CHK/FRE information in user-mode minidump. Only dumps generated from
the new debugger will carry this information.
* Include breakpoint exception in user-mode minidump when the dump is
generated after a breakpoint hits. This enables debugger to show the
current process/thread information when debugging a dump file.
* Fix debugger hang when writing lsass dump files.
* Fix debugging of WOW64 minidumps containing managed code.
* Force the WOW64 extension to convert contexts as appropriate.
* Don't sign extend addresses of 32 bit user mode processes in the 64 bit
* Set 64bit debugger as the postmortem debugger for WOW64 applications.
* Disable adding user-mode breakpoints in kd when KdIgnoreUmException is set.
* Fix escape character ("\") parsing problem in the bl command.
* Force bu breakpoint removal for unloaded modules.
* Add automatic IPv6 detection to the "-remote tcp:..." remote protocol.
* Fix .sleep to work when -ddefer is used.
* Fix .tlist command
* Performance improvements to windbg and other debuggers.
* Notify users when workspace corruption is detected.
* Fix the infinite recursion with corrupt workspaces in windbg.
* Report the correct processor family values in !cpuid for all processors.
* Attempt to breakin only once per ctrl-c, ctrl-break instead of spinning
in a loop on packet write failure.
* Print the target computername in the debugger vertarget output when symbol
information is available.
* Tell debugger users how to break out of symbol loading, if it does not
complete within a reasonable amount of time.
* Display source server spew state when .srcnoisy is run. Also display the
source server only output filter state.
* Workaround for Vista/DWM unpainted captions.
* Add host debugger time when remote kernel target boots and shuts down.
* Symstore: don't truncate long file names when compressing files.
* Symchk: Add recursive symbol search option ("/sr") to force SymChk to
recursively search (non-symbol server) symbol paths for matching symbols.
* Add support in symsrv for getting file pointers from an http store and
using them as is without caching them to the default downstream store.
* Agestore tool should not run on computers that do not update the
last-access-time on files.
* Many !analyze improvements.
* Extensive debugger documentation updates.