I had a question about a limit a customer was hitting with the VM notes using the vSphere (H5) Client. They noticed that whenever they got around ~260 or so characters, they could not add any characters beyond that unless they deleted some. After talking to an engineer within VMware I found out that this is indeed the limit for the vSphere Client today. Through the API, and of course also PowerCLI, you can go beyond the 255 if needed. Also with the Web Client you could do this. If you are hitting this issue, please be aware that it is a known issue and VMware is looking to resolve it hopefully soon.