I agree, this would be a great feature. Nowadays I find myself making the final selection rounds in Bridge because PM lacks this feature, and culling the last photos is so much easier in Bridge when you can compare side by side as you would do with slides on a lightbox back in the analogue days. But Bridge is dead slow compared to PM (LR even more so), and I much prefers PMs metadata tools, so it would be great if I could stay in PM for the entire workflow.