This mission has been planned for a long, long time. There have been several delays for more testing. At the end of the day, it seems that getting the softwar

This mission has been planned for a long, long time. There have been several delays for more testing. At the end of the day, it seems that getting the software right was the biggest deal, but they've done many many simulation runs. There's also a substantial on-orbit demonstration before Dragon is allowed anywhere near ISS. There's still a lot that can go wrong, but almost all of it will result in a decision to de-orbit Dragon rather than going ahead with ISS docking. Nonetheless, <fingers firmly crossed>