You may not necessarily get the same instructor for the whole thing at Kaplan, but you usually won't get more than 2 instructors. Which... yeah... can be bad if you don't happen to dig the way your teacher presents stuff. Then again, you have the freedom to attend another class.
The one thing Kaplan definitely has going for it now is a CBT interface that essentially lets you practice in the exact same format as the real test. As far as I know, the other test prep companies don't have anything similar yet.