Model systems in evolutionary biology

I spend the weekend, with the rest of my lab, at the Evo-WIBO meeting of evolutionary biologists.  Over breakfast we got into a discussion of the role (non-role?) of 'model systems'.  I did my usual rant about how evolutionary biologists don't even understand the concept of model systems, but I'm wondering whether the problem is partly just the nature of evolution research.

Molecular biology, biochemistry, cell biology and physiology have made dramatic advances, largely because many of them work on the same organisms, so that the findings of one study can be directly used as the groundwork for more studies.  Evolutionary biologists (and ecologists) almost always work on different organisms, and although they publish lots of nice papers these rarely can be applied to studies by other research groups.  

This is partly tradition - a mark of academic independence in evolutionary biology seems to be choosing your own research system (organism+field site+questions of interest), but it might also partly arise from the nature of the field.  The process of evolution is intrinsically tied more to variation than to shared properties - natural selection acts on differences, not similarities.  So maybe choosing to work on different systems just looks like the sensible thing to do.

But it's consequences are unfortunate, because although every nice bit of research claims to have big-picture implications, the lack of transferability means we haven't really gotten anywhere.