Disclaimer: I worked at MSFT for 14 years, but that was >10 years ago, in Servers (Exchange, ISS) not kernel. But I've debugged windows stresslab crashes across the network, before windbg got good :)

Is it difficult to transition? Yes, in that if you spend 10 years learning SystemA, then it will take some time with SystemB to build up to the _same level of expertise_ that you enjoyed on SystemA.

The neat thing about learning one OS or system _deeply_ is that the deep knowledge gifts you with frameworks for learning the next-system.

I wrote software on various *nix'es during my university time, then worked on OS/2 (yes, "OS-who?"), Windows, and now I'm at Google, (my work involves 80% Linux 20% Win). It took me some time to re-build my skills on each environment/platform, but it's been a great ride and a lot of fun.

(P.S. earhart@ pointed me to this thread, and says hi to all y'all: Evan, JonO, JVert, LandyW? Dan?)

The most growth (and fun, in my opinion) is experienced when you hop to a new discipline where you have no idea what you're doing.

Source: 33 years experience hopping all over the spectrum

I like to learn new things; I find it energizing, especially when I am feeling burned out. Sure, it can be difficult but that is also what makes it rewarding. It's also really interesting to see the different tradeoffs that have been made between different solutions. (Linux vs Windows for example)

Ultimately, it's all just code and problem solving. And you can usually find a way to leverage your expertise in one domain into a different domain.