At my last company, we installed in-line testers. They worked very well, but there were some issues to be addressed; 1 - Boards had to be cool enough to go through ICT or we had false failures. 2 - We used no-clean flux...enough said about that. 3 - How big a failure queue would we allow before we shut down the line? 4 - Implementing real-time SPC procedures.
There were other issues too, but these were the major ones.
It did not allow us to "get rid" of the ICT guy. They were still very much involved in the test generation and support of boards running down the line, especially in the up-front start-up of the in-line system. It did allow them to free up some time, and concentrate more on the problem child boards. The in-line systems were great. They allowed us to reduce more of the 8 kinds of waste out of our manufacturing process, and to eliminate problems faster, because they were noticed faster.