Thanks to heroic work by the post-doc co-author. She's returned the revised manuscript to the journal editor along with a carefully composed response to the concerns raised by the reviewers. If we're lucky it will be now found acceptable. If we're modestly unlucky the editor will send it back to the reviewer who didn't like it, and we may have to wait a while for their evaluation (we had to wait ages for the reviews and re-reviews of our last paper with this journal group). If we're really unlucky they'll decide to reject it, in which case we'll immediately submit it somewhere else. We think it's now quite a good paper.