Since you asked ...
Dan's a great guy. Intelligent, witty, wicked sense of humor, outspoken in person, difficult to get the best of in conversation, even more difficult to get the best of in training, hell of an awesome teacher, an even better martial artist that has few peers, dedicated, can train all day and into the night, honorable, truthful, sincere, doesn't train aikido but has gone completely out of his way to help a lot of people put Ueshiba's (by way of Takeda) aiki back into aikido, one of the nicest guys I know, etc, etc, etc. I'm sure you're getting a picture by now.
He can not only teach and tell about aiki in an aikido setting, but he can readily show aiki in an aikido setting. With or without cooperation, from anyone. This has been tested by people in aikido up to 6th dan rank. Not only tested, but those people also started studying with him and learning real "aiki".
His students are an excellent measure of how well Dan can teach. You can take any of his longer students (5-15 years) and every one of them is a very capable teacher on their own. Dan not only gets students to *do*, but to understand, and more importantly, to teach what they know and can do.
His abilities are off the current charts. His aiki in an aikido setting is well advanced. IMO, beyond most shihan levels. But, that's just my opinion. Now, add in that he can use aiki in an MMA setting and you realize that his aptitude and skills are daunting to most. But, never out of reach as he has proven multiple times by his students.
If you get the chance to train with him, take it. You'll have fun, work on some challenging solo exercises, meet other aikido people working on the same stuff, but most importantly, you'll start learning aiki as used by Ueshiba via Takeda.