The spirit of using strong typed safe languages for system level programming instead of unsafe languages like C and C++.
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.
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.