I've had a go at Yawg's latest pack, every now and then a few levels whenever I had some spare time, and finally finished them all. The fact that it took me that long is not solely to be attributed to me not having that much spare time; the levels are also pretty challenging!
I have to say apart from the interesting solutions, the levels are also visually very pleasing. Especially 'Mass Lemmicide' and 'Duality' both look downright amazing, while I'm used to rather ugly looking brick style levels.
However these two are not only nice looking, but also feature pretty nifty solution elements. The blocker placement in 'Mass Lemmicide' is rather evident, but in addition to this there are a few more tricks to find. I ended up with a builder to spare, but I'm pretty certain it is supposed to make on part in the solution more convenient to execute. Despite really loving 'Catch 22' with its clean design and well executed main idea (as already stated upon its initial release), I dare say 'Mass Lemmicide' is my favourite level of this pack. 'Catch 22' also has that little downside of the tight time limit making the solution only work after some trial-and-error release rate tweaks (unless there's some cleaner way around this which I haven't found yet). 'Duality' might possibly be somewhat more open-ended solution-wise due to the higher amount of overall skills, but it took me quite some thought to work out a solution, which ended up using a few non-standard tricks. I wonder what the intended solution might be...
After my personal top-3, now a few notes on the other levels:
'Serendipity' seemed a bit too trivial considering the overall difficulty of the pack; I suspect having found a backroute there.
I think I got a different solution to 'Niche' this time, which took surprisingly few tries to execute. Despite the general idea being rather evident, there's still the details to work out, which are not immediately obvious.
'Tilt' had me stumped for a while with the actual solution being conceiled pretty well. It required a lot of precising and timing in the end though, which I didn't like about it.
'Turn it around' required to be saved 0/40 lemmings, obviously a mistake. I assume you are supposed to save all lemmings there.
I sent you my solutions via PM.
Overall a really enjoyable and challenging pack, which I'd recommend to play for experienced players.
Also had a short glance at ClamSpammer's XMas pack, the first level was the only one I managed to solve at once. Will have a proper look at the other three when I get some more time.