Well the thread is a bit old by now but I joined the forum very recently and I have a lot of catching up to do...
Lenny is a student of Haruo Matsuoka Sensei and Larry Reynosa Sensei, both of whom were direct students of Steven Seagal Sensei. Contrary to what some of his students claim in order to advertise themselves as something different, Seagal never said that he has his own style, his Tenshin dojo and the ones affiliated with it are Aikikai dojos. He has his trademark approach and "style" but this doesn't constitute a different kind of ryu...
Lenny is always talking (usually shouting and cursing) about how his Aikido is "Tenshin Aikido" which is different, faster, better, more practical in a fighting situation kind of Aikido but the truth is that this is just a publicity trick, one that has worked well in his favor too...
Whether he likes it or not Tenshin dojo is a traditional Aikido Dojo so there is no difference between his days in traditional Aikido and his so called Tenshin training.
The only difference is that Seagal's approach is indeed more focused on the practical application but he is not the only teacher doing that nor is Lenny the only person on the planet or in Aikido that knows how to use it effectively in a fight.
He is sometimes right about common mistakes done in Aikido schools that diminish the effectiveness of the art but his way is not the only correct one, nor is he the only one approaching Aikido in such a manner.
Sometimes he is claiming that a specific technique is unique only in the "Tenshin style" or that no one does hand deflections the way he does, which is utterly wrong, after all he is not familiar with every Aikido Dojo in the world is he?
Many times he has tried to demonstrate the wrong way that doesn't work as opposed to his own that works... Sometimes he is right, but most times he is watering down the one that is supposed not to be effective, he is showing it making deliberate mistakes in order to prove it wrong and then goes on to demonstrate his own approach.
His Aikido is far from being unique, his whole movement his te sabaki, ashi sabaki, the use of kiri age,suri age and Uke nagaeshi deflections are all Seagal Sensei movements passed on to him by Matsuoka Sensei and Reynosa Sensei. His whole style is obviously Seagal based BUT he lacks Seagal's flow, he is using too much force and he is stiff during his randori probably because he is inflated like a body builder and it's too hard for him to move in a relaxed flowing way...
Now, with that being said, I generally like him, believe it or not, he is fun to watch and I respect him as much as I respect any Aikido person...