The single worst thing in the Elthos RPG is best seen on page 28. That's the list of acronyms.
I hate acronyms.
I will put up with a few of them -- there are, I think, two of them in World Tree. That's a dense 320-page book. I think that ratio is a bit high.
Elthos has, um, 39, except I'd count Exp as a word and 1d6 as a symbol, which are OK.
That's really a lot.
In particular, it makes some of the rules rather hard to read, and some others really boring. (I speak as someone who enjoys reading rule systems here -- the Ars Magica core system is sizzling-hot, for one, and I hope World Tree is too by those standards.) I think Mark knows this, since he's written the English after the acronyms in many places (9, 10), and abandoned the acronyms altogether in others (11).
Even without the acronyms, this suggests a problem. Thirty-nine *concepts* may well be too many for a game this size. Some of these probably shouldn't count against the concept count (e.g., CTR), and a lot of them seem like intermediate results in some final calculation (e.g, DMB), but it's still a lot. The advantage of a short rule set is that it can be really simple to read, understand, and play. I don't think that Elthos is that. It's got more of the feel of the IRS 1090 short form.
There are various things that can be done about this, if Mark considers it to be a problem. (E.g. -- arrange to use ST whenever a strength-based term is needed, and get rid of STB; and similarly for DX and WS. This may take a bit of fiddling, but is often possible.)
Hope this will wind up helping!
-- Bard