I installed SAS 9.2 Phase 2 and EG 4.2 today too. I even managed to run my PROC REPORT custom task (written for EG 4.1) in it, but, although all the GUI, selections and code generation worked fine, the task couldn't find the SAS code to run it! :-(
While full documentation of the add-in model would be good, a list of differences between EG 4.1 and 4.2 would be more useful now.
I agree that the differences between the object model between 4.1 and 4.2 would be good too. Referencing the usual libraries in Visual Studio it's clear there are a few additions ISASTask3 for example. Either would certainly help future development.
More amusing (at least for me!) is that the List Report task supplied with EG 4.2 didn't seem to generate valid PROC REPORT SAS code when I tried it out [SAS uk1076286], so getting my own PROC REPORT custom task to work in EG 4.2 is all the more important! ;-)