Try using the TimeoutSeconds parameter on the Wait-Tools cmdlet.
Some guest OS types might be slower in starting the VMware Tools service.Blog: http://lucd.info | Twitter: @LucD22 | PowerCLI Reference co-author: http://tinyurl.com/hkn4glz
Tried that, but it didn't work.
Anyway, I'm going to close this post because I just found another thread where you are using the GuestOperationsReady property.
Tried that, and this seems to work perfectly.
So, in the end, thanks for pointing me to the other way of doing this, and thank you for your swift reaction !