I went through the "apply now" process, writing the cover letter, clicking forward to see the resume built from my profile, viewing the PDF created from my profile, and then clicking the "attach to application" button.
There was no "you've successfully applied" feedback, and visiting the page for the job posting does not show in any way that I've already applied. (The "apply now" button is still there.)
I don't see anything on my profile page saying that I've applied for any jobs.
I'd like to find out if I didn't succeed in applying so that I can try again -- but either way, the experience was imperfect.