What kind of broad question is that? It's like asking "do salesletter still work?" or "are people still buying from amazon?" Yes, they are. Yes, PLR blogs, depending on what you do with the content, what your keywords are and what your backlinking strategy is, still earn money.
do you mean selling PLR products? or using PLR content? in most cases PLR product blofgs are profitable but for the content blogs... not so much
I think using plr articles on blogging site, it won't give you SEO benefit as these articles may not be indexed in Google because it is already on several websites..
If you meant using plr articles in your blog, I would suggest you to rewrite these articles and make it unique before posting. Here in our DP services section (content creation), there are people who does that very proficiently.