Currently, my HHKB has Hypersphere's rings on it, and the qwerty portion of my girl's Novatouch. As mentioned, the thock is the same, but the clack is pretty much gone.
The Topre sliders have a nub on the end to keep the sliders in place when the keyboard is apart. That's what raymogi was referring to. If you want to take an extra few seconds per slider, a razor or similarly sharp knife can be used to 'trim' the nub, so they still snap into place.
This is the best photo I could find on Google depicting the nub:
The nub serves absolutely no purpose when the keyboard is together. Note, the above is a Novatouch topre slider, which has smaller nubs. The Realforce slider nubs are slightly larger. And obviously don't have the MX compatible portion in the middle