I'm a senior majoring in physics and doing research on the the Epoch of Reionization with a radio cosmology group. Most people, at least in the research group, are on mac's as am I. This, I suspect, is mostly due to them being unix boxes with a nice GUI. I'm not sure what software people studying GR normally use but I end up using a lot of Mathematica, IDL, and Python. My little macbook air seems to work well enough, I can do development, run some stuffy locally for quick tests, and spin all the big stuff off onto a cluster. I have noticed that doing some fun integrals in Mathematica involving QM can easily spike my CPU's for a bit but the convenience is worth it. Something that is easy to take to lab meetings to show people your pretty data is fairly important.

In my experience most scientific software, such as those listed above, seems to be available on Mac/Windows/Linux and work about the same. One downside to running Windows though would be that if you are going to be interacting much with a cluster a Linux/Mac system will allow you to more accurately test things locally such as bash/zsh/fish scripts that fire off your analysis program on a cluster or reorganize large amounts of data. A fairly easy workaround would probably be to just install Cygwin on Windows but I have little experience with that.

I work as a sys admin at a medium sized medical research institute, one of the things I made sure to do was to add nagios scrips to throw alerts for important licenses, certs, and domain names. I'm not sure why an organization as huge as Sony Online would not have added these kinds of checks to whatever monitoring system they are using. Having had this happen to me once nearly a decade ago with a SSL cert I can promise that the 10min of coding to add in a check is much more pleasant than a day of meetings to describe to everyone what went wrong.

I don't often recommend SUN products with the exception of Solaris but Sun Java System Directory Server Enterprise Edition has actually proven to be a very stable solution. I don't believe its open source but I believe it is free. There is also an identity synchronization tool that allows you to sync your LDAP to AD servers if needed. Handles multimaster replication between however many nodes flawlessly with very good performance in my experience. It'll run on Windows,Linux, or of course Solaris.

Good luck, LDAP is a pain in the ass ;)