While the interaction with the Like button may be different, it does allow users to include a personal message when liking content. Often, the message window appears right after clicking the like button, or by clicking on the button a second time. I haven't investigated what causes this inconsistency.
That said, I appreciate the feedback I've received on this plugin. As I stated initially, I have no plans to attempt any workarounds or uses of the undocumented share button in the new API. I understand the problems disabling this plugin caused for some users, but I don't feel comfortable implementing a solution Facebook doesn't acknowledge just to have them remove that functionality in the future. Uncertainty doesn't do anyone any good.