What's this all about? Basically, iap.bin (the name of the new utility) runs on the Duet and allows users to upload new firmware binaries from the Web interface and installs them! No more bossac, no more command line stuff, no more USB needed. Once installed, iap.bin installs any RRF release, including dc42, right from the DWC Settings page. You can install iap.bin the first time via the web interface too (I think you need to be using the absolute latest DWC though for this to work, otherwise you can simply transfer the file to the CF card). I've been switching back and forth painlessly as Christian has worked on the disconnect stuff. It is implemented as the new M997 code and the gcode wiki page has some info on it.
On top of this, Christian has implemented in-place config.g editing in DWC and the ability to upload zip packages. For instance, you can use the zip uploading to upload all of the Duet Web Control files to update DWC.
Here's a screen shot of the in-place config.g editing:
This just in, David Crocker has just released an updated dc42 firmware that includes Christian's iap.bin!