Worth every cent! An absolutely fantastic expansion pack!
Knights of the Nine was rather annoying for a while. Right off the bat you have to go find ALL of the Wayshrines of the Nine (I don't consider that a spoiler. It's pretty uneventful.) Then some of the tasks you have to do seem somewhat ridiculous, but for those I didn't feel motivated, so I just used a walkthrough, because I bought the game for fun and action, not puzzles and thinking.
However, both new quests were still fun, and with the other downloads, it kinda screwed things up. For example (DO NOTE THIS!!), if you want to be "Mr. Holy Crusader Dude", have the Dark Brotherhood over with, and don't buy the Deepscorn Hollow expansion. You'll lose your "holiness" and have to revisit the wayshrines all over again (sounds like fun doesn't it?)
In the end, this game more than satisfied my desire to play Oblivion, and made it even better.