In the Mountain Lion Reminders app you don't have to click the Inspector button (i) to edit a reminder; just double-click anywhere except on the title of the reminder.
[kirkmc adds: To be precise, you can edit the name of a reminder by double-clicking on it, just like any text in a word processor or text editor. But to display the Inspector window, you have to double-click somewhere in the same line, but not on the text. So you can double-click to the right of its name, if it's short, or if it's too long, you can double-click in the margins above or below it, or to the left of it. You can also click on a reminder and press Command-I to get the Info window. The help says to double-click a reminder, which is not quite true.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20120808134056790