There's all sorts of information available on the web about MJER iaido. MJER and its closely related kin Muso Shinden ryu, are two of the largest schools in existence. Several different lines exist with several different people acting as head of the various lines.
You're going to have to do some research and narrow the question down a bit.
Kosho, if the background to your question is to whether the ryu is 'genuine' or not, then answer is a resounding "it'd be hard to find one more kosher!".
I wonder where you have heard it termed iaijutsu tho'? Altho' the terms are somewhat interchangeable, it's more normally referred to as an iaido art.
I started Training in this under Jeff Driscoll sensei about 6 months ago. I really like it and just looking for more info and history. I did some looking into as posted and found out that carl long shihan is my sensei teacher and that Takeyuki Hidefusa Miura Hanshi is his Teacher. So I think I am in good hands with my Training and look forward to learning and growing in this system. I am going down to PA this weekend for some traing and looking forward to it. I did find some Info on the web also, But just wanted to get people's opinion about it.
This means that you are training in the Jikishin Kai, headed in the U.S. by Masayuki Shimabukuro ... http://www.jikishin-kai.com/ That explains where the iaijutsu instead of iaido reference came from, as Miura sensei always refers to it as iaijutsu, so that's the official stance of the Jikishin Kai.
Shimabukuro sensei's iai is some of the best I've seen, and I know a number of really good instructors under him. Jikishin Kai is a good organization with lots of good instructors. I've never met Jeff Driscoll sensei, but if he is one of Carl Long's students, then I would expect his iai to be top notch since Long sensei is very good (I have to say that since I still owe him breakfast!).