It is still relevant, but in absolute terms it's a small portion of how pages are ranked. The PR of the HN homepage is probably pretty irrelevant as I doubt it

It is still relevant, but in absolute terms it's a small portion of how pages are ranked. The PR of the HN homepage is probably pretty irrelevant as I doubt it gets much traffic from organic search for anything other than "hacker news". The PR of your blog homepage has to be taken in context for the type of search terms it might rank for (and remember that PR is for pages, not domains - the PR of your homepage will be different from the PR of each blog article). If your blog was about vegan-friendly fondue recipes, a PR of 5 might indicate you had a link profile which meant you ranked highly because there likely isn't a great deal of competition in that particular niche. If your blog was about dating tips, a PR of 5 wouldn't really indicate anything by itself because it's a really competitive niche.