timppu: Already in mission 11 and 12 Thief 2, and only now I found out there are two quite easy ways to destroy those "mechs" (and other costlier ways). Oh how much I've tried to avoid them before, when all this time I could have just destroyed them. Earlier I thought mines and fire arrows are the only ways to achieve that, and those things cost too much money.
(Yeah and then there is the way to trick the big mech to destroy itself, but that is too much hassle.)
EDIT: Removed the two ways to destroy mechs, in case someone considers that as a gameplay "spoiler". Try to figure them out yourself, aye? I had to read some Thief 2 FAQ to learn them.
Just to help explain the madness... one of the simplest/cheapest ways is found via a note lying around. If you missed the note, I can certainly see how its frustrating, but a nice reward for those explorers ;)
If it helps, I didn't know you could lean forward until my 3rd play through of the game. (of course, once I started doing that the game was far too easy, so I'm glad I didn't know right off the bat).
----
As for me, I'm playing Cognition. Very, very good adventure game with some minor issues that hold it back a bit. Only finished chapter 1 (25% if I understand the episodes). But can't wait to dive into chapter 2 asap.