Google sees inbound links as a vote of confidence, so aquiring quality inbound links can have a huge affect on PR
its good one of my domain changed from pr0 to pr2 as vstar said inbound links will increase page rank
It also revolves around popular sites. A higher PR site linking to your site will have a bigger effect on your current PR. I learnt this today.
it is a great sign.and if you get it higher you need to get more back links related your website theme...
Any PR increase is always a good sign. Who want a PR decrease right? To get a higher PR on the next update, get a good quality inbound links.