True, but as Cillian correctly points out, the RBC is substantially more complex than the hemoglobin that gives it its color.

Not the fault of the Slashdotters, as the MIT Tech Review linked also emphasizes the wrong aspects of this work. If one goes back to the actual paper in Nature, it's immediately apparent that the researchers did not set out to create artificial hemoglobin. Instead, the work is a demonstration of biologically-relevant function occurring in a relatively simple molecule that was *not* explicitly designed for that function. In other words, the protein was designed to ligate a heme and have a hydrophobic core--and that's it. That it behaves much like hemoglobin is coincidental, and that is the point. No design was necessary to incorporate that function. It follows that in nature, life-supporting processes are the natural result of certain molecular properties.

If this protein could eventually find application as an artificial hemoglobin, that's great, but the point of the work isn't to announce the creation of same, but to highlight the fact that there are many potential solutions to any given biological problem, and that complexity of form is not an inherent requirement for life-sustaining chemistry.
So, let's answer some "various questions" from above: 1) This has never been put inside a living creature, and it would likely be toxic in its current form. It would probably require significant re-design (changes in surface properties) to become immuno-silent.

2) While it looks like this is a relatively cheap protein to produce (it's expressed in E. coli per the Nature paper, with nothing exotic added to the media), producing and purifying protein is generally an expensive game. That's one reason why peptide-based cancer treatments are exorbitantly expensive.

3) Assuming an immuno-silent variant, blood type would be irrelevant.

4) The components of pretty much any protein are non-toxic, but it's impossible to know a priori if some fragments of such a protein would aggravate the immune system. Probably not, though, provided (again) an immuno-silent design.

5), 6), etc. .... This protein was created with absolutely no thought to toxicity or viability inside a biological organism. It was designed to test the hypothesis that biological processes can exist in a biologically-relevant framework (a protein, rather than, say, an inorganic metal complex) without being specifically designed-in or optimizing the framework to support said processes.

Even without a ready-to-use artificial hemoglobin, this work is significant because it implies that evolving biological function is a very simple process, and the solutions nature has found to the problems of biology are not the only possible solutions.