i was actually considering the same options: get the new 1,86 with 4gb and 128ssd or get a refurb rev c? My primary machine is a Rev B 1,6 BTO SSD that is now two years old and sometimes takes its time.
I finally ordered the rev c, mainly due to the fact that the cpu is the same, the newer Rev C Models use a much faster SSD that is nearly as fast as the new one and i just need a backlit keyboard... the first benchmarks done tonight show a massive improvement over the old Rev B and not much difference to the new models:
Old Rev B:
http://db.xbench.com/merge.xhtml?doc2=476394
New Rev C with better SSD, more than twice as fast, there could be some improvements after the upgrade to 10.6.4
http://db.xbench.com/merge.xhtml?doc2=477138
and a new one, open gl is the only area where it significanty outperforms the 2008 model....
http://db.xbench.com/merge.xhtml?doc2=476966
Only thing that bothers me is the 2GB Ram, but perhaps Apple will include the bl keyboard on a later revision...
Cheers
Tobias