It is cool but it definitely isn't reliable. For example yesterday we (2 passengers) checked 2 bags each HNL-LAX-LHR-DUB-LCY. The AA tracking said 4 offloaded from (the inbound) aircraft at LAX and 3 loaded onto (the outbound) aircraft at LAX. Yet all 4 arrived in LCY at the same time, and BA in LHR said the bags had been seen by them in LHR when I asked, so they travelled together.

The info is nice but definitely take it with a grain of salt. I took up a lot of a checkin agent's time at DUB trying to insist that one of my bags was likely not going to arrive and asking her to get it chased up, unnecessarily (she was as much help as she could be, to her credit).