I was curious if all styles of aikido use the aiki taiso, or if it is just the styles that were under Koichi Tohei? It seems like all the times I seee them mentioned that is the case, they were all under Tohei at one time.
Also, how benificial does everyone feel about the aiki taiso improving there technique, and how does it help for solo practice?
When O Sensei was alive, Koichi Tohei was the Head Instructor of the Tokyo dojo. After O Sensei's death, he left the Aikikai organization and headed his own style of Aikido, known as the Ki Society. You can read his biography http://huizen.dds.nl/~shiho/aikido/tohei.html
Aiki taiso is generally translated as Aikido exercises. All styles of Aikido do aiki taiso http://omlc.ogi.edu/aikido/dojo/aikitaiso.html
The exercise could be a part of a throw, to practicing forward rolls or wrist streching exercises.
There are two other types of exercise that the Ki Society does, which might be what you mean by "aiki taiso".
* There are ki exercises. These are exercises that subjected to ki testing.
* There is the relaxation taiso, which was developed by Koichi Tohei within the last few years. This specific routine is designed to relax the person doing it and help them achieve mind & body coordination. This simple looking routine has its origins in qi gong and is also subject to ki testing.
Any Aikido exercise could make a solid core for personal practice, but you need to make your practice meaningful. You need to understand why you're doing the motions, especially if the exercise is part of an Aikido technique. You can't just move around, waving your hands and then expect your Aikido techniques to magically improve.