I'm now the proud owner of a working Windows Server 2008 installation (I know, I know, I should have got into the beta but I've been busy..) so I thought I'd have a quick look at what's different in Computer Management. You'll be happy to know that little has been changed within MSMQ management except that there are now two places to do the same tasks (Computer Management and Server Manager).
MSMQ is now a "feature" of the operating system so is found under Features in Server Manager:
I can only suggest that you don't install all 35 features as otherwise finding Message Queuing amongst them may get to be a chore.
Only other change of note is on the "Server Security" tab of Message Queuing Propertries:
where there's an extra option for "Disable un-authenticated RPC calls". This option already exists in MSMQ 4.0 on Windows Vista.
The help explains:
"Specifies whether unauthenticated RPC calls are enabled. Unauthenticated RPC calls can be enabled to support workgroup clients."
Fiddling with this setting changes the AllowNonauthenticatedRPC registry value, a DWORD under HKEY_LOCAL_MACHINESOFTWAREMicrosoftMSMQParametersSecurity
I love undocumented registry values...