I have visited the yoshinkan schools in my area, and it is a world of difference to my aikikai/ki/seidokan blend. It is definitely a hard style that seems (unless I'm mistaken) to rely on some amount of strength to break ukes balance. In talking to sempai, they don't use energy the way other styles do and to me it seemed quite stiff and mechanical. It is, I have no doubt, very effective in a practical sense. (Or the Tokyo police wouldn't use it It seems that what could be termed "ki" development is reserved for dan ranks that have mastered the kihon waza. I have heard Inoue Dojo-cho has incredible energy. But, I guess what I found to be the most interesting is that the yoshinkan probably has the best use of angles and the techniques are very pure to the Founder's original pre-war budo. If someone says that yonkyo doesn't work, have a good yoshinkan practicioner apply it. Their theory of a "bolt lock" makes it a very, very practical and effective technique.
Just my humble opinions and observations
Hmmm... OK, I'll bite on this one.
If you'll permit me, I'd like to quote myself.
This is a portion of an e-mail I sent a friend (and aikido author) regarding Yoshinkan. I'll add a few additional comments at the end.
I think someone once said that once you've seen Yoshinkan, you'll recognize it from then on. That's very true, I think.
Yoshinkan is based on exacting, precise movements. Beginning Yoshinkan practitioners look very stilted -- almost robotic -- in their movements. Hell, not just beginners!
To me, Yoshinkan is both a style of movement AND a style of teaching. In many dojos of other aikido styles, I have seen Sensei demonstrate a technique 3 or 4 times, and then you get up and practice.
In Yoshinkan, techniques are subdivided into a series of well-defined steps. You learn and are taught precise movements and positioning for each step of a technique.
Step 1: enter with your right foot, just off the line of uke's attack, while turning your wrist just so.
Step 2: cross-step with your left foot, driving your left hand up, etc...
I have heard this accurately compared to doing one of those children's "connect-the-dots" puzzles.
In Yoshinkan, you learn techniques by learning where the "dots" are in each technique. So, (beginning) practitioners look very stilted, because they move step-by-step, rather than in a flowing motion. This is particularly true when one is learning a new technique, but you'll often see it in standard practice, too.
Shite (called nage or tori in other systems) may do a step, check to see how (or if) they've affected uke's balance, make any corrections, then go on to the next step, performing the entire technique in this manner.
In this way, shite can learn the subtle differences in movement between actually taking uke's balance, and just moving to "about the right spot". You learn how to be precise and exacting in your movements, and get what one might call a very "technical" education.
As Yoshinkan practitioners get more advanced, they learn how to do techniques more smoothly and in a flowing manner, while still retaining the precision with which they learned it. I liken this to "rounding off the corners" of the exacting, almost mechanical way the techniques were originally learned.
That's seems to be the opposite approach from other styles, where I have seen other aikidoka learn to be fluid FIRST, and, as they get more advanced, THEN learn the details and precision to make techniques "work".
Note that eventually both styles of aikidoka end up in roughly the same place: smooth, flowing movements with exactingly accurate technique. It seems to be just different paths to get there.
There are some physical differences in how techniques are performed, but in general the underlying principles are the same (take balance, move from your center, keep connection with uke, etc).
Just a couple of months ago, Susan Dalton wrote a good article in Aikido Today Magazine about Yoshinkan. I think it explains a lot of things, and dispels a few myths as well. I'd recommend it as good reading.
I could go on, but this is probably already too long. I hope this diatribe was somewhat helpful to understanding each other.
As always, this is just my opinion based on my personal experiences. YMMV.