I always try to maintain an open mind. Since I primarily work with the Oracle RDMS, I always try to keep myself familiar with its competing products such as MySQL or Postgresql. Yes, I am better at some platforms than others, but if you lock yourself into one platform, then you can very possibly become obsolete over time. I used to be a Windows-only guy. Over time, I've experimented with Linux as an Oracle DBMS platform. Now that I am very comfortable managing Oracle on Linux, I find that it is my preferred platform by a large margin over Windows or Solaris. No, I don't run it on RHEL like a lot of shops. I run on CentOS for one simple reason: free updates, and no cost involved. Yes, Oracle doesn't support it, but it DOES run on it. CentOS is a binary equivalent of RHEL so much that Oracle identifies it so and installs just fine, and runs the same. I don't have to pay for maintenance & support or updates. My Oracle platforms are rock-solid as they would be on RHEL. A few people in the office are wary of this, but ultimately it comes down to me and I am the one supporting the environments. We have not had ANY issue that required an Oracle support request in the past 10+ years. If we did, I would setup a separate server with a trial of RHEL, install Oracle, and try to replicate the issue on the test environment. It has never come to that though. So, we get the rock solid platform we need, at ZERO cost.
To clarify before the flames begin: We are not a typical "production" Oracle shop. We are an ISV whose marketed applications run on an Oracle back-end. We develop our applications to utilize the Oracle RDBMS, and in-turn, we are a member of the Oracle Partner Network (OPN). We pay a few thousand a year for our OPN membership to use the Oracle RDBMS in a development environment. We pay extra for TAR support access as well, but rarely use it. If we had a live website using an Oracle back-end for order processing, etc, you can BET I'd be running on RHEL with RAC with full production licenses. But again, that's not in our solar system today.
The same thing goes for our virtualization platforms. I primarily use Hyper-V R2, but also use VMWare ESXi for server virtualization. Hyper-V costs almost nothing, and ESXi costs absolutely nothing. On the desktop virtualization front, we use VMWare Player for our QA and support teams. That costs nothing as well.
It's win-win in my eyes, as well as my boss who happens to be the CFO.