I hesitated to add a rating, given how so many others have noted their troubles with it, but after a little research, I figured out why. While lots of themes have some kind of pagination built in, plenty of others don't. This plugin works off the built-in pagination, if your theme has it, and pretties it up. If you don't have an ugly version of pagination already included in your theme, you'll have to go code diving and risk messing it up if you don't know what you're doing. My advice is to use this plugin only if you (a) totally know what you're doing code-wise, or (b) see ugly little pagination numbers in your theme and want to make them look nice and stylized. If you don't know code and don't see any pagination feature in your theme, you'd best skip this plugin or find a different theme.
The one issue I have with it (the reason for 4 instead of 5 stars) is that longer numbers tend to fall outside the boxes in the stylized pagination. Still, it's so much better than the pagination my theme came with, and I love it.