I went through most of the levels now (excluding the ones posted after the deadline), only missing Internection Cube (made some progress, but then moved on to stay in sync with what Simon was playing) and Magic of Lemmings (still don't have a good idea how to contain the crowd).
I think my favourites so far were Clown Fiesta (seemed completely impossible at first, a lot of interesting ideas to piece together, and yet the execution is easy and not much need for experimentation to see what works and what doesn't. Had a blast with this level.), Primitive Instinct (again, seemed impossible first and a lot of interesting observations to be made, but here a bit more experimentation was needed to determine how many builders are needed for what, and to discover that the lone flimsy root prevents building from the diagonal bar to the wall with 3 builders), and Skyfall (not hard to see what's going on, but somehow very elegant).
Splash or Splat seemed very interesting, but I might have skipped some of the intended steps; the Instrument was cute; Supreme LEMCO Safety Standard had a lot of interesting ideas to find but also a lot of fiddly placements and timings, felt super tight and I might have appreciated some extra leeway.
I especially had fun playing with runner skill. 
I probably have found some intended solutions and backroutes.
I attached replays for all lix levels!
Glad to hear that! I was afraid "The Last Shall be First" may be a bit frustrating due to all the timings to get right. This one and Pommes Schranke are intended, for Hanabi I released a small update to prevent one element of your solution.