With r20024 I can get ibrowser to actually download the Mozilla webbrowser control. It usually takes a few tries, often the download hangs halfway through. I have the feeling that it helps if you move the mouse constantly during download, but that could just be my imagination. To install the control, you will need a copy of MSVCP60.DLL, which the author forgot to include in the install image (Wine has the same problem). So first copy MSVCP60.DLL from your Windows installation to \ReactOS\System32, then start ibrowser, download the control and install it. After that ibrowser (and the "Web" button in ROSExplorer) becomes functional.
GvG