So I got a Keso 4000 which I can play with. It has been quite some time since I set my eyes on them but it took some time to get to know them. (And will try to get a Kaba gemini for comparison too.)
I'm not sure whether or not the following violates the rules or not. I did not write anything on how top open or pick them, but I'm still not sure whether it's allowed. Hopefully admins will let it though.
So for future reference about KESO locks:
For those who are not at all familiar with this kind of lock they are dimple locks with 3 line of pins. (from the 2 sides and one on the edge of the blade.)
The Keso 3000 -1000 family can be easily differentiated from the 2000-4000 line: The uneven thousands have a rhomboid shaped key.

The 2 sides are symmetrical the key can be with both sides "up" but for me it seems the pins on the opposite sides do not "test" for the same dimple.
One of the things which is already clear is that the KESO has a few different kinds of pins. The lock I taken apart had 5 different kinds. It's funny though: the key's dimple cuts are pretty much all the same. There are a few which telescoping pins like the Mul-t-locks, but for me it seems there are single pins shaped like a telescoping one too.
Another thing is that the key's cut are interlocking. Which means two dimples are meeting each other.
One point to keep in mind is that the key has lot more cuts than needed, probably to somewhat complicate copying but it's surely primarily for master keyed systems. As far as I know the unneeded cuts are made locally not in the main factory.
The interesting part is the floating interactive pin in the tip of the key.This is called the omega pin. It works by pushing the corresponding pin in the lock with just the right amount of force. Notice that the interactive pins in the key might be pressed inside the key. It's not really that complicated basically 2 moving pins with a spring in between them. I'm not sure whether there is a difference in spring strength,but otherwise it wouldn't really make too much sense. (If my description didn't make it clear to you you should check out Keso's homepage which has a really good picture. Look for the part describing the omega function.
Another nice feature is that where the key's blade meets the bow right where it begins to get broader. I'm not sure what is the English terminology for that so let's call it collar. This key's collar has a step like a broader shoulder which is thinner than the rest of the key at the top and at the bottom. This part never goes inside the keyway but instead meets the lock's outer surface right above and below the keyway. The lock's face has a corresponding longitudinal groove in which this thinner part can fit in. An ordinary key could not fit in since it's too broad and it couldn't get in deep enough. Also if you try to manually make a key thinner I think it would severely weaken the key.I made a somewhat clumsy attempt to bump it which resulted in a broken key. Though it might simply be because I'm not well practised in this. So impressioning didn't worked out for me.
A few things stuck me as nice features: The lock is very precisely made. The tolerances are very tight, everything fits neatly together.
The pins are made of very high quality steel, not even in the same league as brass. I have no scientific equipment to test them but they are extremely hard.
This lock was one I really liked. AS I slowly gathered infos about it the blind love went away, I can see a few possible problems with it, but I still hold this lock dear.
I'm ridiculously bad in picking as of now, and also I'm not sure whether it's for the open forums: so even if I really wanted I could not give any good advice: all I say to pickers is that I found the springs a lot stronger than the usual ones.
I will also upload photos once I figure out how.
I'm looking forward to getting my hands on Kaba-s. I expect them to be very nice locks too, but I'm very curious about the differences.