I don't find it important but it makes like hard for the likes of me and no doubt others. To many people put to much weight on the green bar so when it come to link exchange it's hard to get a good site to exchange links as your pr is not high enough. Daft thing is you can have a pr0 site getting more visitors than a pr5
Google shows this bar horizontally, Firefox - vertically. It's only a matter of preferences. In any case, it that so important to know your PR? Its only a factor of prestigiousness.
I like having the search box function mainly - but do want to see the TBPR of some sites... If I'm really interested in their credibility I click the Get Data button on my SEOInc toolbar and investigate from there.
I'm always curious of a sites PR and backlinks. And I like having the search function right there at all times. Comes in handy.