400D still worth it?


Depends on how much it is selling for.

A much new camera like a Pentax Kx (2nd hand) is selling for about $500.
Look around the BnS for the other brands as well for good buys for some of the newer models (or wait for some of the folks more experienced with Sony, Nikon, Oly, Canon to give inputs on 2nd hand prices for the other brands)