Maybe there is some dirt or other crap causing some friction in the spacebar. Model M spacebars ought to feel exactly the same as the rest of the keys.
Nah, no dirt or anything there, checked that. The problem lessened some time ago when I removed the spring and put it back again in the process of trying out a Model C2 spring. Now it resembles the other keys more except it flaps a bit like an ailing bat but that's it. The remaining problem is that the stabilising isn't very good and right side caves in as opposed to the left and there's general wobblliness. But it's less and less noticeable the more I get used to the keyboard.
Yeah, the MX-11800 bothered me for a little bit when I first got it, but I did get used to it.
I have two of those: one from Cherry with blacks (currently typing on it, which is fun--I'm getting better at avoiding bottoming out while still registering hits and it seems better than on many a tactile keyboard as long as I do score the hit at all) and one with browns from Compaq, the same I need to visit my techie neighbour with in order to get the switch from Pause soldered where space is.
Incidentally, my current experience seems to suggest that linear switch with reduced force would probably be the best thing for me. Like all of them doods actuating at 30g, no tactile, no audial, no nothing. Then I'd probably be reasonably happy. On the other hand, I notice myself missing the tactile click after using an M for a longer while, although typing lightly without it on blacks is way fancier and I feel more like a pianist.