In your dealings with them did you notice any similarities to your system of Aikido?
It's jujutsu, like aikido, so you will have a great deal of overlap--SHIHONAGE, KOTE GAESHI, IKKYO, etc. But Atemi-ryu folks work in a lot more nastiness. Whereas in aikido we normally take someone to the mat and pin, they will do techniques to break them in four places before taking them down and then pantomime breaking their neck, e.g. No doubt many aikido players would find this objectionable.
If it needs saying, Atemi-ryu folk are focused on street application where technique is concerned. Gus himself seems personally interested in philosophy and spirituality, but makes no bones about the fact that he wanted to be able to hurt someone in a violent engagement. Something I found very insightful about his teaching is how he would distinguish situations and appropriate applications, e.g., "Do this if it's five guys in a deserted parking lot, do this if it's your cousin Frank drunk at sis's wedding."
This group has taken some pretty enthusiastic body slams on various internet fora due to claims on Atemi-ryu websites other MAs find questionable. I don't even get into that debate. But what I found consistently while on the mat at Gus's or at seminars in Miami with Chenique or Moses Powell, was hard work, sincerity and respect. I quite enjoy training with them.