Benefit: Generating full 1:1 previews
will help when you zoom to 1:1. They don't help as you move from image-to-image, unfortunately. You'll still see the "loading..." message.
However, you will see much faster "pop" response time for the image to become clear after you enable the zoom. 1:1 previews can be beneficial if you do a lot of macro work where zooming to inspect detail is a common part of your workflow.
Anti-beneifits: They are an overhead issue with your catalog and can bloat the size of it. Your best bet for day-to-day work is to let LR generate the standard previews, and then when you zoom, LR will generate the 1:1 as needed. According to Martin Evening, the longer you stay in a folder with the images in question, the more 1:1 previews will be created. One other thing - it will take much longer to import your images if you generate 1:1s on import. Go out for dinner if you do.
LR can be set up to help keep your catalog size down by deleting the 1:1 previews after a designated period of time. Or you can keep them. If you use one catalog as is now the common wisdom (my catalog as over 130k images and keeps on truckin), forcing the creation of 1:1 previews will bloat your catalog for sure.
Marty