I have been given the privilege of publishing during the Beta test period in the Open Access journal The Winnower for no cost but my time and care.  I was also given assistance by the International Journal of Astronomy and Astrophysics to publish my work on massive star formation there.  A work unrelated to the first two, on the LCDM model is in press at ScienceOpen Research.  All of these are Open Access Journals.  Two have open peer review and all have post publication commenting.
Here are some good reasons that serious researchers at any career stage should consider such journals in preference to traditional outlets. 

1.) Open and public access will ensure that your work is available to anyone who may be able to benefit from your findings.  Furthermore scientific work is supported either directly or indirectly by public funds.  We seek grants from the government for our specific works, we are employed by institutions of higher learning which are funded in whole or part by government funds.  Our students often are supported by student loans which are in turn paid to us via their tuition.  Very little science is paid for with 100% private funds these days.  Even industrial R&D is done by students and research faculty now. 

If you truly believe that what we all do is for the greater good of mankind then why should most of mankind need to pay $35 for the right to read our results? Especially when mankind pays our bills via their taxes.  

2.) Open and public review ensures that comments must be backed by concrete reasoning and detail.  Rather than benedictions with Papal force, the reviews are conversations in which argument from authority is not even an implied part of the text. 

Prior to submitting the first article in a series  regarding a new approach unifying Quantum Field Theory and General Relativity to The Winnower I did submit to a well known scholarly open access journal.  This journal which is associated with a well known institution/society of people who study physics.  It does not matter which one.  Rather mysteriously two of their three reviewers said this work was "incremental" but encouraged me to submit to another journal.  I did not ask incremental building on what.  The third said it did not make sense to him.  With my paper on massive star formation I submitted to a journal associated with a similar society of Astronomers, I was encouraged to submit to another Journal since they only publish new observations not work derived from other observations.  

These good responses were friendly if critical and brief.  While it is possible to respond to the reviewers it is rarely useful.   No reasons or detail are given to respond to.  In public peer review this will not work. 

3.)Public reviews can be responded to publicly.  The general population can then see the scientific process work in an organized way. Rather than thinking publications are instantly final and settled science they are revealed as what they are, communications and nothing more. 

On The Winnower in particular anyone may comment and review.  The force of their review relies on the persuasiveness of their arguments not any authority they may have.  Anonymous reviews such as those on The Winnower can protect the reviewers from scorn.  However anonymous reviews automatically loose some credibility points.  Further so far no review has offered a really credible argument against me which I have not been able to answer.    One of them went too far and contacted the places that employ me all of which have offered me even more classes next semester. It has been said that for The Winnower and other publications like it a review is much more like standing to comment on a conference talk (ScienceOpen Blog "Where did our Peer Review Mojo go?").  I find this to be true. 

For example if the BICEP2 paper had been submitted to a journal like The Winnower or ScienceOpen Research all the public comments on it would be consolidated at those places with the paper.  The evolution of the paper through its various versions may also be tracked.  The arXiv where it was published does allow for blog trackbacks.  This can serve the same purpose to an extent. However, a more formal system has many benefits. 

4.)Early career researchers can get publications for their new and original work.  This is particularly true in the Theoretical sciences. 

Theoretical sciences, such as Theoretical Astrophysics, Theoretical Particle Physics, etc can be subject to a great deal of subjectivity.  Often what gets published and where are influenced not by mathematical rigor, numerical precision, or logical consistency but by who's writing, where they work, and what they work on.  

For example, for many years those who wrote on the theory of Loop Quantum Gravity complained that it was much harder for them to get publications especially for their early career researchers.  If this publication model had existed at the time that problem would have been less of a problem.   Now they have fewer issues as the second superstring revolution has died down.  For a time if one questioned string theory at all one was a heretic.  Surely the LHC would switch on and evidence of large extra dimensions and SUSY would fly out.  Meanwhile it seemed that if one added strings branes and SUSY to any model it would get published.  To an extent it still seems that way

5.) Open Access Post Publication Peer Review undermines those who would seek to dominate scientific discourse for their benefit and via their accumulated authority. 

There are many examples of works being published based on who someone was in traditional journals with not facility for public comment.  Work which was as often good as bad but with unquestioned authority of name and placement their ideas would suppress Early Career research.  If journals like ScienceOpen and TheWinnower had existed in the Early 20th Century then Piltdown man would have been discredited as Raymond Dart published freely about Australopithecus Africanus.   Instead authority was able to keep that fraud alive. 

Most of the time this is not so baldly fraudulent as it was with Piltdown man.  Most of the time it is simply a fact that those who were reviewers in the traditional system were the very people who's life's work would be undermined, superseded or made redundant by new research. This persistent condition should if anything undermine the credibility of traditional journals not enhance it

These venues are not perfect. 

One thing I would change about the Winnower would be the ability for reviews to use the same Latex and publication infrastructure as papers themselves.  Complete with giving a DOI to reviews. A featured borrowed from ScienceOpen. ScienceOpen has an expert pre-screen which is closed this would also be opened up.   IJAA and the other SCRIP journals have classic pre publication peer review.  Those journals would allow for a period of public comment after the traditional review but while a paper is in press.  

That said, Open Access, and Open Peer Review lead to better science both  in content and procedure.   The scientific method is one which was always meant to be practiced in the Open.  Journals such as The Winnower bring us back to that basic truth. 

TL;DR: Don't fear change but embrace it with due caution and enthusiasm.  Science is at heart  all about carefully executed change in knowledge.