Hi MPCDI,
in vSphere 5.0 I was quite unhappy with VDP but as I'm running 5.1 now for several weeks the VDP seems to have improved a lot. I currently use it to backup about 60 production VMs and it's running quite smoothly.
The only real point of criticism I have right now is the logging and error reporting. The logs are scattered all over the VDP appliance and the log analysis is really annoying and time consuming. Most times you won't see an error on the web client UI telling you why the backup job didn't succeed. It just says it failed and you have to go very deep into the appliance to analyse the problem (you can of course open a SR everytime a Job fails if you got time for that).
So I think VDP needs some improvements to keep pace with 3rd party vendors, but it's not that horrible anymore as some may say. Also I haven't tested VDP 5.5 yet, so my comments only apply to vSphere 5.1
Regards
Tim