Does "Vista Ready" just mean that the skin will load on Vista, or is it supposed to mean that the skin will look good on Vista?
This mean the Skin as been made for Vista and XP or Vista only. It meant the author/skinner create the elements needed by Vista.
is it supposed to mean that the skin will look good on Vista?
This is a wrong question
Skinning is a mater of tastes and Limitations in Vista Case especially.
Some things good on XP will looks really bad on Vista. we can't expect the author/skinner will do the "same" exact skin on Both cause for some skin it's necessary to change some elements/settings to fit Vista limitations.
When that said,You could also have a different point of view on how do this or this than an other people it's normal.