Hello Ashley,
Ive spent about 5 hours tonight trying to resolve what was supposed to be a "simple" upgrade, clearly this "major re-write" has some "major bugs", heres my findings so far..
Simple update is called "simple" because it really is - it just downloads the vanilla Host msi installer from the web and then runs it with a silent key/parameter. The Host installer is exactly the same file as available for manual download on the
download page, except only it's distributed via Amazon Cloudfront servers for faster delivery.
If you have issues with Host service not starting after simple update, that may be due to various reasons but all of them have a "system" nature outside the product itself. Sometimes restart of the system may be required for the service to "kick in", and that in turn may depend on specific services policy on that computer. Sometimes,
Recently, we had a support case with a customer who hadn't updated Windows for about a year and their Windows Defender engine (just the engine, not the threat databases, which was weird in itself) was outdated. Windows Defender prevented the Host service from starting after the update and not after the fresh install. Once they updated Windows (and Windows Defender for that matter) the problem was gone.
I highly recommend that you add the Host installation folder to antivirus software exceptions list to avoid future problems in this regard. Far too often modern antivirus software is incapable of distinguishing between a benign program and malware so it makes sense to think ahead and eliminate this problem before it arises.
= Not sure what they did to the keyboard, but i can no longer type in ANY VMWare console (vSphere client), they numbers work (top row) but the letters do not, again this was working fine in the past version, so what was changed to break VMWare vSphere client typing (which is 90% the reason i use this, its on a machien onsite that has vSphere or vCenter install to log in to 20 servers, now i cant log in to any of them as i cant type in to vSphere (even after restarts).
We added an additional keyboard input model and made it default. This model is used by any other top remote access software and it's kind of standard. However, you can still switch to old model for specific connections in your address book by selecting this checkbox:

Hope that helps.