I am not completely thrilled by MCCs.
For one thing there's the startling slowness with which the Twiddler spits out the keys.
If you manage to squeeze in another chord before it's finished the second one doesn't show up.
Unlikely with bi- and trigrams, I admit.
Then there's cognitive load.
MCCs are definitely something to get into after achieving some fluency.
For example, Kent Lyons found MCCs provided only moderate improvement, possibly because his subjects were still learning.
To help with the load I think it is important that MCCs be meaningful chunks rather than arbitrary ngrams.
I can think in terms of characters, words or syllables, but my muscle memory has trouble deciding between chords for, say, i and ie on the fly.
I'm definitely with @AlexBravo on the trailing space issue.
For cognitive reasons but also because space has to be a fast chord anyway.
And what's the use of 'ing ' in swimmingly?
(Yes, backspace is sure to be fast as well, but it's getting over-complicated.)
More fundamentally, I see MCCs as a last resort application of unused chords.
If the riches of the chord space are better exploited then there are fewer chords left unused.
By bringing shift and control functionality into the chord space, thumbless makes fuller use of it to speed up a wider range of single characters, and has less scope for MCCs.
This works extremely well for keystroke-based software development.
If you type mostly natural language (ie punctuation and upper case are relatively rare), or mostly point and click, then thumbless's trade-offs may be the wrong ones for you.