For an excellent example of how a clean object model can solve extremely difficult technical problems, check out LMAX's "Disruptor" framework: http://code.google.com/p/disruptor/

By rigorously separating the concerns into a clean object model, LMAX achieved a level of performance which might correctly be labeled "miraculous". http://screencast.com/t/g67kFj8nRue

It's written in pure Java. Amazingly, I haven't found anything that's achieved better performance thus far. It's very elegant.