I have just upgraded to 8.5.1 and am now having problems with the Eclipse based Help system in the Notes client and Designer client.
It takes an age to load the Help Contents. Then when I do a search it takes a long time. About 5 seconds for each of these tasks. Then it takes about 10 to 20 seconds to actually load the page I click on in the results.
Meanwhile the old-school Admin client help fires up and responds instantly.