Or do you think that's totally a waste of time for generating buzz and trying to get more traffic ?
As an ex-journalist, let me tell you this. If your aim is to get your company or product written about in news media (newpapers, magazines, professional blogs, etc), posting a press release with one of these PR-sharing websites won't do you any good at all.
Most journalists are inundated with press releases. Most releases wil get at most a quick glance before being discarded. A journalist is unlikely to read a release in detail unless it is from a company or an agency that he knows and trusts. The idea of a journalist actually going to a website to look for releases is ludicrous.
As for video news releases, this seems even more absurd. When I worked as a journalist, the concept was unknown, so I can't comment with certainty. But the idea of any journo taking the time to sit through a video seems highly implausible.
So, to answer your question: No, posting PRs on line won't give "more buzz", nor will it generate traffic. And it certainly won't get you any exposure in the media.