It has been some time since I had looked at the Auto Deploy and Host Profile feature in vSphere. As a former customer, I still remember one of the challenges I had in evaluating Auto Deploy and specifically Host Profiles was the fact that it did not cover all the possible ESXi configurations. This made it very difficult to operationalize as you still needed to handle post-configurations through other mechanisms. Trying to keep both solutions did not make sense for me and I ended up opting for the traditional scripted installation method via Kickstart which I had hooks into automate the full ESXi configuration.
In vSphere 6.5, there was a huge effort to significantly improve both Auto Deploy and Host Profile to what customers had expected of this feature, especially around bringing parity between the configurations that could be done using the vSphere Clients and/or vSphere APIs into Host Profiles. In addition, there was also several UI enhancements that now makes it possible to use both Auto Deploy and Image Builder directly from the vSphere Web Client which was never possible before. For more details, be sure to check out the What's New vSphere 6.5 white paper here.
One new feature that I think is worth calling out is the new Script Bundle capability in Auto Deploy. Previously, if a particular configuration was not available via Host Profiles, there was nothing you could really do and you had to write your own custom post-deployment script to apply to the ESXi host. As I mentioned earlier, in vSphere 6.5, we have closed the gap on the ESXi configurations that were not possible using Host Profile and will ensure that will be in sync going forward. Having said that, there are still certain configurations that are not possible today such as creating a custom ESXi firewall rule for example. For these cases, you either had to either hack it up using a method like this or to create a custom ESXi VIB which would then force customers to lower their ESXi's software acceptance level which was not ideal nor acceptable, especially for customers that are security conscious.