Keep away, unless you are one of those teenage types who insists on using arrays of smileys and other useless punctuation. Extremely annoying to the receiver and has been linked with all sorts of other cr@p being installed on your machine unawares.
Most compelling is that it uses its own file format which is a sod to export out of. I had to purchase a copy of ABC Amber Incredimail to export messages from a client's mailstore and import them back into mainstream outlook PSTs.