I know this topic hasn't been posted to for a while, but if you're interested, I have upgraded my 8900 with OS 5.0.0.411 from Vodafone DE on crackberry's site. I've had it for about a month, no problems period. It is an official release for European nations. Also, I am using BB Desktop 5.0.1
As Kickstar13 said, this is just a few tweaks here and there. But it enabled visual voice mail after I enabled it on TMO thru the phone. And it does work on my 8900. I've also got better signal by this upgrade. I will be glad to answer any questions. Hope this helps other users of the 8900.