So I have been trying to get together some hands on 4.1 videos for you guys (and girls)
however KB1011292 has been my main reason for not upgrading.
What is KB1011292 I here you ask?:
"VMware View Composer 2.0.x is not supported in a vSphere vCenter Server 4.1 managed environment as vSphere vCenter Server 4.1 requires a 64 bit operating system and VMware View Composer does not support 64 bit operating systems.
VMware View 4.0.x customers who use View Composer should not upgrade to vSphere vCenter Server 4.1 at this time. Our upcoming VMware View 4.5 will be supported on VMware vSphere 4.1."
As you know the supported way of upgrading your vSphere enviroment is like this:
1) Upgrade vCenter
2) Upgrade ESX hosts
3) Upgrade vmware tools
4) Upggrade vm hardware version.
Therefore if you run VMware View 4 with composer your trip into 4.1 greatness is going to come grinding to a halt with step 1.
Having VDI is great however it makes upgrading a pain...so roll on VMware View 4.5 with your 64bit composer.
And for those not tide to VDI here is the Vsphere upgrade guide: