The writing is real easy actually. The quality of the character recognition differs between softwares, but the Sonomama jishyo amazes me sometimes with its ability to guess what I want out of my often garbled handwriting. You can also adjust the time you get for writing; I have Sonomama on fast which means it will guess a character after half a second of not writing on it.
Kanken DS doesn't recognize as well as Sonomama, but if your stroke order is correct that will usually do it. Sometimes I'll draw a kanji that looks damn near textbook, but since I didn't do it in the right order I get something else.
One of the main features for Kanken is the comprehensive exam they give you for each level that's meant to simulate the actual kanji test that folks take in Japan (I forget its name, but its similar to the JLPT but for kanji only). The first time you take it for the day will determine your grade, so if you fail it they'll actually flunk you and make you repeat the last grade! For example, after passing enough tests at level 9 (you choose from 10, 20, or 40 minute-long exams) I unlocked level 8. I thought rock on, gave it a shot without practicing it in the training sections and flunked it, so they knocked me back down to 9 and I was unable to take 8 again for the rest of the day. The following day I passed more tests in 9 and 8 was made available again. Makes for some intense kanji quizzin'.