It wouldn't necessarily prevent a patent from being obtained, but it would protect SpaceX from being found in violation. I know this from first hand experience.
When you combine this with Trade Secret law you protect yourself from one of your employees taking your technology, starting a new company and patenting it (potentially coming in under the 1 year mark).
First-to-File only comes into play when multiple entities file for overlapping patents, it simply finds in favor of the first to file for a provisional patent. This avoids a mess of trying to determined who came up with the idea first, which was always a contest of who documented first.
[1] You could still be in violation and not know it as provisional patents are non publicly disclosed for 18 months, so in reality there is technically a 2.5 year window where you can't be absolutely sure someone else has filed.
Anyway, another thing that many people miss on the "first to file" issue is that it's the first INVENTOR to file. So, employee can't leave company, steal the invention, then file if employee was not the inventor.
The law really is only changing in the situation where two people invent the same thing, independently of one another. Under the current law, if both inventors file, only one is entitled to the patent - the inventor who actually invented it first (perhaps determined in an interference proceeding in the patent office or perhaps in court). Each inventor would try to prove the date of invention through documentation (keep those lab notebooks - or that git repo, or the old svn or cvs repo backed up!). Whoever successfully proves an earlier date of invention wins.
Under the new law, it's just who filed first. If two people file for the same invention, there will be a "derivation" proceeding in the patent office to determine whether one of the inventors "derived" his/her invention from another (ie, is that person actually the inventor).
Do you specialise in software patents?
Although I do write software patents for some clients, my practice is more broad than that. I deal with patent, trademark, and copyright (intellectual property) issues, as well as contracts regarding software, books, art, and ip issues. I also handle litigation about all of those issues.
If you think that you have a poor understanding of the law.
So, on most legal blogs, you'll see something that says "I'm not the reader's lawyer."
The period to file was supposed to be important though in non-conflicting applications. It allowed, for example, potential applicants to seek investment in various ways without fear of a specified disclosure causing loss of priority. Do you know how much inventors availed themselves of that ability?