I also disagree with adding 'Mithril' to the game.
I can certainly see the point of giving the elves some better materials for their elites and heroes, but mithril from trees? Mithril was invented by Tolkein and most people will be imagining that metal (which does *not* 'come from trees') when it's mentioned. If the elves are to be given an advanced material I don't think it should be named 'mithril'. After all, mithril is not an old word (like, say 'Elf') and is not ambiguous in its meaning. Using the same word to refer to a different material to the light, strong silvery metal that is mined from deep in the ground is just confusing, misleading and pointless.
I also am not convinced that the non metal-using elves should get a super metal or that metal from trees makes much sense. Some kind of super-wood (the adamantine of woods I guess) would make much more sense and fit much better with the elves. Or perhaps they could simply get an edge with magic when it's implemented.
*This next section may contain spoilers. Do not read it if you don't want elements of the current DF ending given away*
Besides... here's a summary of what I know about mithril from Tolkein:
It's a silvery metal that is very rare, valuable and coveted by dwarves (and probably others, but the dwarves especially are willing to take big risks to get it in the books). It makes very light, strong armour and weapons of exceptional effectiveness.
The dwarves find a mountain containing it and create a large fortress/mine/city thing. This makes Moria the glory of the dwarven world. Then they dig too deep and release a demonic monster that destroys the fortress. Leaving it abandoned and inhabited by monsters, a trap for adventurers who might awaken the great Evil living within.
And here's Adamantine in DF:
It's a cyan-coloured metal (so not 'dark' as some other products have it but light and, perhaps, shiny) that is very rare, valuable and coveted by dwarves (and probably others, but the dwarves especially are willing to take big risks to get it in the game). It makes very light, strong armour and weapons of exceptional effectiveness.
In the game, the dwarves find a mountain containing it and create a large fortress/mine/city thing. This makes your fortress the glory of the dwarven world, with the King travelling to live there. Then they dig too deep and release a demonic monster that destroys the fortress. Leaving it abandoned and inhabited by monsters, a trap for adventurers who might awaken the great Evil living within.
So, I don't see that 'Mithril' adds so much to the game. The story of your fortress is closer to Moria than anything else I've read and Adamantine seems to take the place of Mithril... although by using a word with a less clear-cut definition Toady get the flexibility of getting to tweak the properties of the metal without misleading the players. So, why add mithril? It's already basically there.