So if your 32-bit Domino server is already on a 64-bit windows box then you are probably going to be OK. However, I would always want the path to be my choosing. An in place upgrade of this nature might leave a 64-bit Domino server installed to D:\Program Files (x86)\Lotus\Domino and that’s just nasty.

So I am very much in favour of the new h/w approach. In fact I’m considering doing a VMWare P2V of the current server and then migrating back to the ‘reformatted/rebuilt’ physical infrastructure.

Technical:
I never said you can’t upgrade in place, only that I would advise against it. If you read the technote you quoted you will see that the 64 bit installer actually de-installs the 32 bit version first – that has been the case since x64 Domino was released though I admit I failed to note that in my original article. If you are going to do an un-install and then install over it my premise of ‘garbage in = garbage out’ still stands. Upgrading in place a server that has been around for any significant period of time is not something you will find allot of experienced Domino admins advising to do – unless there are some very important reasons.
If you are goign to re-use the existing HW (or virtual box) doing a n uninstall and then cleaning up any remnents of the data and old settings is always a good idea beecause it will make sure you are not pulling in old, unnecessary settings and configurations.
Any additional opinion/comments?

Answer: Install 64-bit Domino over your existing 32-bit Domino.”

It worked.