If raw PR is still used in the algo then showing an accurate number (3 significant figures) in WMT would help SEOs backwards engineer it.
The toolbar PR (which displays to 1 sig. fig.) is a pretty useless metric in the grand scheme of things. If you want a single, simple metric to act as a health check then you'd actually be better off looking at the number of root domains linking to your site (which is far from ideal).