This is a very high-quality, useful app. I love being able to customize the colors, I like being able to do my own labels, and the tags feature is inspired. I've been tracking my mood on paper on and off for years, but iMoodJournal is extremely convenient, makes the data easy to interpret, and is just fun to use. It covers all the basics you'd expect, including reminders, plus a lot of nice extras that you can use or ignore.
I've been trying out two other apps that contain mood journals, Pacifica and MoodKit, and while those apps have additional features their mood trackers aren't nearly as customizable or enjoyable to use (although Pacifica's is a 6 point scale rather than 10, which some may prefer.) MoodKit's in particular only lets you record one mood per day (who only has one mood all day?), which is not a problem with iMoodJournal.
Update: well, not a whole lot has changed. The map feature is kind of neat. I have reminders set to random and sometimes I get two in one day and sometimes I don't get any, but otherwise iMoodJournal works so well I don't care. I've been using it for two years and am still quite happy with it.