I'm not the only one either it seems. I've talked to a few others and I've had a good look around the internet. There seems to be a very high percentage of people with 8.5.1 installation problems.
The problems themselves are varied. In my case, I got the core product working (after an extremely long installation - that bit, apparently, is common to everyone) but although I got the Administrator client running, the designer (and really my only reason for interest in the upgrade), simply refused to start.
Other people seem to have different problems and indeed there's a whole list of them in the comments on vowe.net. (http://vowe.net/archives/010922.html).
I tried uninstalling, deleting folders, running NotesKill and a whole host of other things to no avail.
A History of Bad Installs
What makes this particularly annoying is that after years of having (in my own words about version 3), "the worst installation program of any piece of software on any computing system", IBM/Lotus was finally starting to get things right. Now, they're right back to square one with the first installation program I've used in years where I've had to give up on the product.
A Matter of Timing
The other problem of course is the timing. Of all the times to have a bad installation, IBM would have to pick the version which they've released FREE** to developers.
So, have I lost faith in Notes? No, I guess I'm a sucker for punishment and every company is allowed to have at least one Vista or one Windows ME moment.
I'll still be here to report (hopefully) astounding success on perhaps 8.5.2 - Hint: IBM ... don't even think about giving us a post-install fixpack.
** Don't even get me started on their definition of FREE.