i've narrowed down the scope of the question to something more specific in a new question:
-- end of update.
I have legacy code, written in 9.3. makes extensive use of arcobjects, now the company bought 10.2, and after updating all urls, it turns out that all arcobject calls are no longer supported, and it seems we have to write a server object extension, which is discouraged even in esri's docs, to wrap the old code.
Am I missing something here? are arcobjects calls really no longer supported in 10? is there a way to reuse the old code that I might be not aware of?