I have not used the new Motorola development studio, because my experience with Motorola's development tools has not been a joyous one. When working with Motorola devices I tend to stick to the standard emulator (or sometimes the Sony Ericsson emulators as those are the best I have worked with by far).
The problem with Motorola's tools is that I always seemed to spend way too much time trying to figure out how to work around them. I would run into emulator specific issues and bugs, and I honestly don't have time to waste trying to figure out why the application runs on the target device but crashes on the emulator. It should be the opposite.
A good emulator is very important for mobile development though as that is where you will do 90% of your development, testing and tweaking, only periodically trying it out on the phone.
Finally, I agree with bpapa...Netbeans is an excellent IDE for J2ME development and here is a book that I recommend (get the original if possible, not the second edition as the second edition focuses way too much on MIDP 2.0 and assumes you know the basics).
http://www.amazon.com/J2ME-Game-Programming-Development/dp/1592001181/ref=pd_bbs_sr_3?ie=UTF8&s=books&qid=1221692983&sr=1-3