In highschool, I wrote a tiny toy kernel, running solely in 16bit real mode. Quite fun, but I wanted to go further and my knowledge was lacking, although the project did help me learn a lot of ASM.
The OP has shown that I could do all sorts of cool stuff going straight into x64 without all the incantations! That's actually super exciting, and makes me hate EFI a little less ;)
I'm going to go play, I think! I wonder what Lisp would be the best candidate here...
http://www.ocp.inf.ethz.ch/wiki/
There are still some students and external guys keeping the ports going.
http://www.ocp.inf.ethz.ch/forum/index.php/board,4.0.html
Nowadays, I think Oberon spirit will live in Rust, D, Go, C#. :)
D - Xomb - http://wiki.xomb.org/index.php?title=Main_Page
Go - TinyGo - http://code.google.com/p/tinygo/
C# - Singularity - http://singularity.codeplex.com/, Cosmos - http://cosmos.codeplex.com/
The main problem is lack of support, it is a very big effort to create an OS and it is very easy to turn attention to other stuff.
Linux and BSD distributions wouldn't have reached the state they enjoy nowadays, without the help of the existing UNIX toolset and investment of companies interested in seeing the projects succeed.
In terms of the language, the Oberon 2 language report is 17 pages of which 1.5 pages is the full EBNF for the grammar.
Then again, looking at the new stuff from the people keeping Oberon alive, it seems much less interesting to me as well.
I did like Oberon a lot, as a GC enabled safe systems programming language with module support, and the ideas of Native Oberon exploring Smalltalk dynamism in a static compiled language.
As for Wirth's minimalism, specially the latest Oberon-07, I don't like it that much.