From what I've read, it looks like Kiko is different because it offers some fancy Ajax drag and drop features. Ajaxian has a good review of the features:

* Appointment reminders via email, text messages, and AIM
* RSS feed for upcoming events
* Natural Language Quick Create (ex: "3/26 2am Raid on Ironforge [WoW] +thrall +gromhellscream")
* import appointments and contacts via iCal and vCard
* and personal public URLs for your calendar.

Here's some screen captures taken from Kiko...