What are VMware tools and how important are they in your VM's? Is it just a bunch of drivers or will it turbo boost your VM's?
These are the functions you get with VMware tools:
1. The memory management driver. This is "vmmemctrl" for the memory ballooning mechanism. From VMware Best Practice Guide: "If the virtual machine’s memory usage approaches its memory target, ESX uses ballooning to reduce that irtual machine’s memory demands. Using a VMware-supplied vmmemctl module installed in the guest operating system as part of VMware Tools suite, ESX can cause the guest to relinquish the memory pages it considers least valuable. Ballooning provides performance closely matching that of a native system under similar memory constraints. To use ballooning, the guest operating system must be configured with sufficient swap space".
2. Guest OS clock sync. Depending on your VM's, you may not want to use this function. Especially for AD servers! If you have a structured NTP service, this feature it nice to use, but not necessary.
3. Mouse & video drivers. The video driver is important to have since a VMware SVGA adapter gets install on your VM. This is not important for the VM to run, but it will be to manage the VM when you need to remote into it! The "VMware pointing device" also needs drivers to function!
4. Heartbeat of the virtual machine. This service or daemon can alert administrators in vCenter about problems with a particular VM.
5. Drivers for each OS.
So there is nothing on this list that will "turbo boost" your VM. All the tools provide is management and drivers for your virtual machines. But what if you have VMware tools install and they are just out of date? It will probably be safe for the VM to function. But, VMware does update the "vmmemctrl" driver and the heartbeat mechanism in different releases. These functions are important for the management of the VM itself. Also, when VMware tools are out of date, you may not be able to control functions for that virtual machine via vCenter, which in turn may interfere with PowerCLI scripts.
I find it best practice to keep the VMware tools up to date. I have not seen any case where VMware tools has interfered with the local operating system. You can also choose the option for your VM's to install the latest version when the VM reboots, but make sure your environment doesn't have a change control process that would require oversight of this process. Make sure you follow your company's process for updating a VM in your environment (that's the ITIL in me).