It sounds like it is somewhat safe to use blockchain.info again.
I would also say this just shows the importance of rigorously testing any new release of any software that in any way controls any kind of money because people may not immediately continue the upgrade cycle after a 2nd release is released to fix any potential problem
I haven't seen any sign that they have fixed the organizational problem that created the technical problem.
According to other reports, they have a single super-programmer who ships changes without independent review.
If that is true, good luck...
That is probably not a good idea. Regardless of how "good" someone is at their job it is always important to have people check behind workers' work in order to make sure it meets a certain quality standard.
Although it would generally not be a good idea to have one person (or even one team) in charge of such programming, it would still potentially be feasible as long as a completely separate group is able to independently test and audit the code prior to it being released