In the computer industry, especially now, it seems like it is never a good time to upgrade. There is always something to wait for. Most people will tell you to wait till March right now for R600. Which is probably the wisest move.
On the contrary, I myself just purchased an EVGA 8800GTS and can't wait to receive it along with the new system I'm building. The wise move is to wait till March, but I am buying a new 20.1" widescreen and wanted a more powerful graphics card then my plain X800 128MB card. The card will be awesome, no doubt, but it may end up on the losing end of the DX10 first-gen card gamble. That's not to say it won't be a great card, but the R600's may be even much greater, or at least drop the 8800 series prices some.
Anyway, I'm going to enjoy my extra month or two (or more if stock is limited in March), and move on. The E4300 looks like it will be easy to OC and its price just dropped $10 at zipzoomfly, which along with my failing pc, is enough reason for me to do it all now. I'm sure in March there will be some new nvidia to wait a month or so on anyway.