I have just now baked some Normal Maps in 3ds Max and at first I used a Cage for every object. It resulted in some skewed and squashed detail which I deduced to be caused by the Rays not being shot perpendicular to the faces, but slightly angled, due to the difference between the Object Vertex and the Cage Vertex. I then did a RTT without a Cage and there was no skewing or squashing at all. But also, all details were sharper and the whole object looked better. Now it is possible that my Cage was rubbish, but anyway...it made me wondering...

Do you use a Cage for baking Normal Maps or not? If you are, what's the benefit (save having to limit the length of the Ray with a numerical value without a Cage)?

Depends on the object. I normally do it without and if I find I need a cage I turn it on. The cage is nice because it allows you access to each of the points so you can noodle them around to fix problems (or cause them heh)

When I add a cage I normally end up resetting it and pushing it back out. For some reason the default cage is always trash to start with.

One very important distinction in max is that, when using cage(as apposed to the offset tick) the cage normals are averaged, even if you have hard edges. This is a pretty wonderful thing, because it means you can render seamless results even with plenty of hard edges(smoothing groups) on your lowpoly.

It also means that the ray direction will be wonky around large angle changes, so you may need to add in more geometry, manually tweak your cage, or do 2 bakes(cage and offset) and composite them together to get the best of both worlds.

Me personally i prefer to just add some more supporting geometry, imo in most cases this is the best solution because you dont ever need to bother with manually adjusting cages. Manually adjusting cages can be a real nightmare if;

A. you change your mesh at all
B. you have to transfer your work to a different app to bake

Also its worth noting that many problems will "skewed" or poorly aligned details can be fixed by making the LP line up better with the high, in the case of round things this means adding more sides etc.

I think in max 2008 onwards you can export your cage to an editable poly which gives you a bit more freedom when editing the cage. As long as you retain the same vert index you can import it back again.

After that i usually use paint deformations to push verts out while retaining the original normals.
Not sure if this is the best way to do things, have had mixed results.
I think the trick is to keep the cage smoothish, so you dont have big differences in ray distance between neighbouring verts. Again not sure, i have only baked a few normal maps.

Somethimes i get better results just using Xnormals ray distance calculator and a blockers file.

For best results add more geometry to catch the high poly normals.

if someone else is going to use this object you are doing and redo something on it, better not using the cage, or maybe if you want to export to maya, or vice versa, better not to... or for an example, u want to use the xnormal for the ao and bake the normal maps in max with different cage, not good.

resuming, i never use cage.