I think this was an experiment by the Olympic Committee, I think it was a good idea to allow Pistorious to compete this time, he wanted to compete, he is good enough to do it and do it right and it was good for the sport.
I do not think it is unfair for anybody but Pistorious himself but if he is up to the challenge why not?? Obviously he did not blow up the competition and broke the world record or anything like that, so in his case the blades are not a big advantage. Also, It is possible to know the benefit a person would get with these devices, for instance you can calculate the extra impulse he may or may not get with them, so it is not hard to regulate the use of them in case others with similar cases want to compete too. He is just too good to compete in other disable people so the next step is to try with the fully able runners, for now this is his only option, other than to not compete at all. I think that for now is ok, and they should allow him and others in similar conditions to compete as equals as long as they qualify, if in the future if it is observable that there is in fact an advantage with the use of artificial legs and there are enough runners with artificial limbs then you can separate them but for now I think is more than ok.
I really do not see a reason in not to allow him to compete with regular runners "just because he is different".