I've only integrated reporting the results from running automation. I'm currently doing using ADODB calls and writing the entrys directly into the DB. What I've done is as part of DDT, I've added testlink id's, testplans, and build into the tables. When reporting the results, I insert into the "Executions" and "CField_Execution_Values" tables the results. If you decide to go this route, the thing to keep in mind is all the data is essentially in node_hiearchy table. So you basically have to do alot of joins on that table.
I'll probably switch over to using APIs after the next major release. I'm sort of avoiding the APIs right now while it's still in Beta because I have no idea how it'll change in the future, they've really been making some radical changes in the APIs to date.