How intricate :P I got the real demo and played through it during break this morning. I'll post feedback and replays in case you want them, but let me know if I shouldn't post them publicly yet and I can remove them.
Level 1: Decent level but pretty simple. This would work well as an early level.
Level 2: Not sure if this was intended! If so, it was a very nice puzzle, looking thoroughly impossible until I spotted the trick.
Level 3: Perhaps a bit simpler than 2 but still very imposing at first. It was a tad annoying that the brute-force route (bash, build, climb, bomb, mine, walker) fails by a single pixel and there's another red herring route that fails by only two; but in both cases it was clear enough that the routes couldn't be made to work, so I didn't spend much time on them. One feature I particularly like -- I've spoken about this before in discussions of the walker in general -- is that you don't know beforehand how it will be used, so it's plausible to examine routes where it's used differently.
In general - any level I've posted publicly, it's acceptable to publicly post replays and/or feedback for (even if I haven't posted my own replays yet). Of course, don't assume any other author applies the same standards - that's just my standards.
Will post feedback shortly. :)
EDIT: All three solutions are intended, though it's possible to complete the second one much faster.
Bomb the blocker, when the worker is at the highest point of the clump with the steel block - this does NOT have to be particularly precise. If you do this, the timing for the rest of the level should fall into place immediately, instead of having to wait many cycles for everything to line up.
Based on feedback from you and from a tester, I think I may have to reconsider the position of the 2nd demo level; I think I've underestimated its difficulty.