I actually got to try the variable Topre keyboard from EK, too. It was a great keyboard, although it does take a bit to get used to the variable weighting. The Topre feel is very different from MX Switches. The actuation is very high, practically near the top. After that, the key smoothly "collapse" into the bottom with a very nice solid sound. I think the PBT keys and the overall build really lend to the premium feel of the keyboard.
That said, even with the slightly heavier feel, I think I'm more prone to making mistakes on it compared to my heavier MX Clears on my Keycool 108, which is by far my favorite Cherry switches.
That being said, the KUL 87U does feel a lot more solid than my Keycool, and I'm tempted to get the KUL 87u if I can find a separate NumPad with MX Clears to go alongside with it.
I use a Logitech M570 trackball and what I want to do is to place the trackball between the tenkeyless keyboard and the tenkey numpad