Looks fine by me!

The long horizontal range is definitely useful for the spear. I generally think constructive skills will be more effective in the horizontal dimension; with the destructive ones, i.e. the grenade, I'm a little more fixated on the vertical dimension (like bombing from below, denting a ceiling for a Shimmier etc.).

Thus, the Grenadier with the current arc will still only work on comparatively low ceilings, but it's high enough that I think we could design level terrain specifically made for this (without that terrain shape giving away too much about where to assign which skill).

I generally don't see that much use for throwing a spear against the ceiling, HOWEVER there is one big Shimmier-related one, the counterpart to the "Grenadier hole dents the ceiling to stop the Shimmier":

If the spear lands in the ceiling diagonally, forming a little ramp, the Shimmier can land on it and start fencing or maybe even bashing from there. Especially the Fencer at this point would be useful, because it allows to precisely what we would currently need the Laser Blaster for: A way to carve a path into a ceiling for a Shimmier to continue.

In this case, the Shimmier could carve that path himself, whereas in case of the Laser Blaster, you'd need a different lemming to do it. Of course, in the former case, three different skills are needed (Shimmier, Spear Thrower, Fencer), whereas in the latter, you only need two (Shimmier + Laser Blaster).

Thus, I don't think this type of Spear Thrower usage would make the Laser Blaster superfluous. I'm just saying it would be a way to work around this if, for some reason, we would end up not getting the Laser Blaster. (Which I don't think at this point, since it seems to be the most popular skill at this point.)

Well, I assume this is just an issue referring to the Swimmer's position trigger:

While the trigger is inside water, the lemming will always try to move to the top of the water area.
While the trigger area is outside the water / in the air, the lemming will be a Faller.

Thus follows:

If the slope never causes the position trigger to leave the water at the bottom of the trigger area, then the lemming should indeed not fall, but turn around and go back up, as the water area would force him to do, and as it is right now.

If however the slope causes the position trigger to leave the water at the bottom of the trigger area, the lemming should automatically turn into a Faller.

This is indeed something I was also confused about when I first discovered it while making my very first pack, Paralems - and one of the reasons why the level "Skies aflame" (which happens to have upside-down water, but as namida and Proxima have said, that doesn't affect its functionality) requires a Basher at the end to get the Swimmers out of the water, instead of them falling down at the bottom of the water area.

Especially when designing levels with the Speedy-Eggbert tilesets by Jaimie (Techno and House), this is confusing, because in the actual game Speedy Eggbert, falling out of the water when you reach the bottom is exactly what happens.

However, I'm not sure how many levels would be affected by this if the behaviour were changed now. My level "Skies aflame" would be one example (though I'd say that particular level would change for the better, since that's what I originally wanted). I can't name any other examples off the top of my head, though I'm sure there will be at least a few.

This is tricky - because it's very much dependent on whether we end up getting the Laser Blaster or not :

If we don't get the Laser Blaster (even though I consider that unlikely), we have no way of modifying the ceiling for Shimmiers. So if the Projectiles should fill that gap, the arc would probably have to be steeper than it is right now.

On the other hand, if we do get the Laser Blaster, then I think a more horizontal arc, as it is now, would provide more incremental use for the projectiles:
The Laser Blaster is a skill with vertical range (well, of course, if it's a 45 degree angle, it's just as much horizontal as vertical range).
The Projectiles, as they are now, offer more horizontal range.

I can agree; Lemmings Migration was one of the first packs I played. Stumped me for a good while, but eventually, with some slight hints, I managed to beat it.

Of course, that was at the very beginning of my forum presence. For you, the pack will most likely be eay too easy. But it should still be fun to play, and also to watch!

Has the text on the post-level screen been shrunk? It looks much narrower and more in the centre.

I'm not a fan of this. Again, too much empty space, in this case on the sides (and for what purpose?).
I'm used to the post-level text spanning the entire width of the screen.

Thanks for the overview!

Regarding wall jumping and the note "what if lemming is also a Climber?", as said before, I'd keep this consistent with L2 behaviour, in that the Climber always takes precedent over the Slider when wall jumping. Meaning, a Climber-Slider jumping at a wall will start climbing up. He will only become a Slider when falling down from the top.

Yep, seems fine by me!