George S. Ledyard
Irimi is at the heart of all martial application. If you go to a dojo and no one can enter without you hitting them, the practice is ineffective. That's my first test... I frequently arrive at dojos to teach and find that not a single student can pull off an irimi when I attack. That's because I REALLY attack. at the majority of the dojos I see around, the students are not really trying to strike their partners. If everyone trains that way day after day, they think they know how to do things they really cannot do. As Frank Doran Sensei says, the "entry" is everything, everything else is just icing on the cake.
Anyway, it's a shock when a bunch of third or fourth dans, or even worse, someone running a dojo, finds that they can't do an entry. They can know 500 techniques and without effective irimi, it's just 500 techniques they cannot do.
The second thing one can spot at a dojo at which the practice is clearly martially ineffective is closely related to the above. Can the students at the dojo strike? With speed, with power? If not, then the practice is being done at unrealistically slow speed. People will not be able to adjust when it gets fast and hard.
What does the "intention" feel like during practice. Once again, you can look at the folks in many dojos and see that they have no projection, no forward intention. You can stand in front of them and feel nothing. They have no idea how to organize a strong forward flow of attention. If you attack them fast, or God forbid, with unexpected timing, they are never ready. You can stand in front of someone like this and know you will hit them before you even start.
One of my students gave me a book on the theory of limits as applied to business. While being over my head math-wise after about three chapters, I got the gist of it. It changed my thinking about how we teach our art. The theory of limits says that in any complex system, like a factory (and Aikido is also a complex system of body / mind skills), one needs to analyze the various elements that go into producing the output of the factory and decide which one is the "limiting factor". You can throw all sorts of money and resources into that factory and have no increase in the production whatever if you don't devote them to improving the "limiting factor".
So, in my opinion, most Aikido practice is done without any regard to this idea. People are studying a wide range of techniques, empty hand and weapons, putting all sorts of time and money into their training with almost no increase in actual skill from year to year because they have not addressed the limiting factor in their Aikido.
For the majority of the folks I see training, the limiting factor is the lack of ability or willingness to train with attacks which have speed and power. Strikes have no body integration and hence no actual power. Grabs tend to be "strong" in a way that is totally ineffective. A grab should be designed to effect the partner's balance and his ability to respond. Turning your partner's hand purple by grabbing really hard has no martial effectiveness whatever and is probably making you tight in a way that limits your ability to move freely.