When I observe most people practice Gekken, the main focus that I see is to just win. What I mean by this is plain and simple, just trying to score a point to survive. This normally will lead to using movements that are not real technique, but performed in a manner to score a point. This will lead to a tag a thon for those at the basic levels of Gekken.
One of the most important things about Gekken is not to win a point, but how do you win? Instead of coming up with techniques to score a point, are you trying things that you have learned from class? Most practitioners do not see how the things that you have learned in kata can be applied and you can still win. If done properly, you can see how much presence and pressure that is taught in kata can defeat the opponent.
For myself, what I practice is to only use the techniques and factors that I've learned through kata and win. Throughout my years of practice, I feel like I've been able to get to the next steps.
The I believe the best way to explain the levels :
First level was to just win. As I mentioned above, it was just about using blows, movement and plain physical ability to land a blow. It's just attack attack attack. This is what I see most often and I consider this lower level. You can see that this will lead to ai-uchi or when both practitioners strike each other at the same time.
The second level was to still win with physical ability, however starting to apply the kamae, strategy, and the techniques that were taught. I discovered how much more efficient it was to project what I've learned and still being able to win. You can start feeling it "click". Less movement, less attacking, "controlling" your opponent. For me, if I was sweating a certain amount after Gekken practice, I considered that I was not fighting with good technique. (Funny thing is I wrote about practicing this level way back!)
The third level was when you really understood the technique. When done properly, you do not even really need to attack. You can sense that you were able to make your opponent hesitate for just a moment. If you watch the kata of many koryu, the correct technique is only applied when the enemy is manipulated to attack first rather than you attacking first. The technique that is used is not the actual strike, but to control the opponent.
I believe the level explained above is where you can control your opponent, apply your technique, and when done properly, you do not need to make contact to make your opponent feel the "loss". You can stop your Gekken sword close to the target, and they sense what the result would be if they continue to fight. Either they do not feel comfortable to attack, or you don't need to make a victorious blow. This is what I constantly try to practice for myself.
When you experience and can understand that feeling, you then begin to understand the spirit of "Katsujinken" or life giving sword. My goal for myself is when I practice Gekken, it is to strive and gain that spirit when I take on that challenge. This is what I believe truly separates Gekken from playing tag even when using the same equipment.
For me, even when I see another practitioner perform the higher level techniques as I explained and expressing themselves, I can truly feel it in my heart!