Steve,
I'm just one data point, but I think I prefer the old method of photo expansion (click, then expand inline). This one is really obnoxious when you consider that it launches on an "onmouseover" event. Further, it really does not allow you to expand photos inline with the text so that you can easily view the expanded photos *while* reading the corresponding text -- this plugin takes over the entire screen. There is also a significant delay (for me) from the mouse hover event to the launching of the photo (granted, this is on a dual-core 1.6GHz netbook, so not the fastest of machines).
I could be missing it, but I don't think it supports the option to forward the viewer to the maximum quality image in the user's Gallery either.
Just my $0.02. YMMV
Any chance such a feature could be configurable on a per-user basis so that we can use whichever method one prefers? That would remedy my objections but it may not be practical.