Hopefully the point will be moot in the near future. If I had a chance to publish a paper in Nature or Science, I'd probably go for it (because I'm vain, but so is everyone else). Other than that, I don't think I'm going to publish anything that isn't open access going forward. It's a touch more expensive, but worth it, IMO.
In my experience open access is considerably more expensive. Maybe it depends on the field and the journal but places like PLOS often quote something upwards of $3,000 for publishing, and closed-access(?) journals are, ya know, usually free to submit and publish. I could be wrong about that though, and I do know that many open access journals and universities offer price reductions and financial support for cash-strapped scientists. Not only to account for the fact that there's still a strong negative bias towards open-access journals in many scientific communities. A lot of (older) researchers still view open-access as a "pay to publish" sort of deal. I think that'll change over time, and a lot of younger researchers seem much more receptive to open access publishing, but it's hard to convince up and coming researchers to use open access journals if they know that it's going to negatively bias the senior researchers in their field.
I'd say the same, but I have yet to have the discussion with my current adviser about open access / bioarxiv journals. I was wondering this morning about Science / Nature publications though. Most universities like to put out press releases / videos on paper publication, but without a clear date, it gets more wuzzy. Do you start promoting your researcher's work as soon as it's deposited on arxiv? After the reviewers okay it? Once the journal has formatted it and redone your figures in illustrator? It's honestly a sort of stupid concern, but one of yet a number of ways in which scientists would have to adapt to and agree upon if this was truly the One True Way forward.