Right, I have been playing around with the timeline and animation options, and here are some of my conclusions so far.
First, I have not worked with a similar timeline before in other animation applications. It is plain different, and has its good and bad points.
First, this is a pure frame-by-frame animation timeline: no automatic tweening in sight. Second, the animation timeline in the PRO version is limited to a mere 24 frames length. The EX version is required to remove this limitation.
The workflow, once figured out, is actually really simple, and quite effective.
1) create a timeline
2) create an animation folder
3) create layer groups and/or layers in the animation folder to hold content
4) assign those layer groups or layers (called "cels") to frames in the timeline
5) the timeline supports the standard operations, such as dragging and dropping, (drag)selecting frames, copying, pasting, and so on.
It is also possible to start a new animation project, which can be divided into stories, scenes, timelines, cuts, and so on. An option for timelines to be named automatically according to scene and cut name is also available, as is managing all the files by using folders in the project. This is actually quite nice, I think.
Being able to quickly group layers in the animation groups and maintaining cell name integrity is also quite nice. And I do like being able to do whatever I want in a cell group. It's easy to layer a cell quickly.
Also neat is the fact that any frame in the animation timeline can reference any cell in the layer panel. This makes it easy to re-use existing cells. Right-mouse dragging over a range of frames allows for setting a cel for the entire range. Interestingly enough ClipStudio remembers the length you set with this when a new cel is assigned to the next range - no need for right-dragging. Very handy for animating on two, threes, fours, etc. The next frame is automatically selected, so it takes no time at all assigning cels to frames this way. Pretty cool. (Btw, the manual uses the term "cel specification" for assigning cels to frames in the timeline. A bit of an awkward translation.)
I also like being able to drag in the view with the timeline tool to scrub through the animation.
Another handy feature is the Animation Cels panel, which allows for comparing/use a light table for any frame. So two entirely separate frames can be compared easily, and used for drawing reference.
Clips are also available in the timeline, and easy to work with. Time stretching, for example, exists as an option.
Initially I thought having all those frames in the vertical layer stack would be a pain to work with, but it actually works quite well, much to my surprise. The timeline scrubber controls which layer is selected, so it is not difficult at all to locate a particular cel in the layers. The layer search dialog allows for quick filtering of particular layer types, which include animation folders and animation cels.
I had success importing an Anime Studio rendered uncompressed AVI file in the timeline.
Things I thought could be improved, or I plainly disliked:
No sound support! No ability to import sound in the timeline is a fairly serious omission, in my opinion. At least, I could not find an option to do this. My attempt to load up an AVI file with sound failed.
The onion skinning in TVPaint and Krita is easier to control, and offers more control. I am not saying the onion skinning in CS is bad - not at all. Quite good, but I still prefer the control I have in the other apps.
Other things are missing as well: for example, I could find no way to reuse a cel in the timeline, and just re-position it. It will re-position all the cels in the timeline. Perhaps it is possible, but I could not figure out how to do this. If not possible, I feel this hampers the workflow a lot.
No automatic frame colouring.
Sub/child-animations which are re-usable across the timeline is another option missing in action.
This is pure frame by frame animation: and the things which seem to be oddly missing in CS, are readily explainable after realizing another animation product exists: ClipStudio ACTION. These two work in tandem, and ACTION does include camera control, sound, and tweening. The Japanese site explains these two are supposed to work together.
Seen in this light it starts to make more sense: Clipstudio Paint EX is meant for traditional 2d frame by frame animation. It does a pretty good job in my opinion. The one thing I really miss is sound import.