One big reason for me to switch to colemak and touch-typing (from qwertz and hunt and peck) was that the lessons were composed of real words instead of nonsensical clusters of letters like in the standard qwerty lessons and in parts of the lessons you linked to. Typing real words lets me concentrate and focus on the lesson to a much greater extent and makes learning more fun. Also, you practise words which you will use later on for 'real' typing, which conveys the impression of actually learning something useful right from the beginning. The lessons you linked to seem quite interesting though, although I will definitely miss out on the 'introducing' and the first part of the 'comprehensive' lessons! Thanks! I wouldn't, however, recommend using them for learning cmk, as they don't introduce letters in any logical or relevant order for that layout. Something the cmk lessons also do is convey the message that many words can be typed solely on home row and even with the 'first' 4 letters (left middle, left index, right index and right middle, ie s,t,n,e).

One thing I don't like about sentence lessons is that as you practise the lessons you get familiar to the sentences and start to know the off by heart, which boosts your typing speed, but for that very text only. Of course this is only relevant to you if you are planning to time yourself.