We have recently made the switch to EFPS.
It is a Frequentis system and the displays are Wacom tablets, and our version includes a writing tool, in the form of the above-mentioned stylus, a device about twice the bulk of a ballpoint pen.
It is very difficult to write neatly. If the strip is enlarged, and then the writing carefully applied, an acceptable result can be achieved. The distraction involved in performing these actions often makes it not worthwhile.
There is a four-colour option, and it is more akin to writing with a crayon than a pen. In addition, there is a parallax error, because the writing surface is a plexiglass-type screen maybe 3 mm above the actual strip. When the stylus has been recently calibrated, it is reasonably accurate - along the line of calibration (top left to bottom right: there are only 2 calibration points) provided ones head doesn't bob around too much. (And, of course, aerodrome controllers don't move around at all, do they?
)
Exacerbating this is the minor detail that the strips are considerably smaller than the paper ones, so there is a lot less room for writing, and the layouts for where stuff has to go is different. Accuracy is required with the stylus to open the correct item on the strip. Miss it, and you might end up having to close a dialogue box, and using the "undo" function to make the correction.
I believe quite a lot of the inherent problems with using this system rather than nice, simple, reliable, tactile low maintenance relatively inexpensive paper strips could be partially mitigated were the writing tool considerably better in function. (Precision, definition, no parallax.)
It also randomly stops writing on the odd occasion. For no discernible reason. Maybe out of memory for the particular operation? Moving the strip/re-enlarging it solves this problem. It is then just a simple procedure to glance at the strip board, then the radar, then maybe look out the window, and re-acquaint oneself with the traffic picture and ones prior train of thought so that the safe movement of lumps of aluminium might continue.
There are some things E-strips does reasonably well. Handwriting is not one of them, and we mainly use it for rather simple symbols, such as a line/arrow combination, or a
H in a circle, that sort of thing.
It is easy to clone strips on the system, or create new strips. Usually faster than handwriting them. If it was not necessary to look out the window from time to time, it would enable one to perform
almost as efficiently as the paper strips did.
Another aspect that most controllers seem to find frustratingly limiting is the serial way information is required to be actioned. A strip cannot be accessed while a dialogue box for any other operation is open. One process at a time, worked through to completion, then on to the next thing. Not so good in the dynamic and (in the past) somewhat free-flow multi-task, reactive environment that aerodrome control is.
Maybe I'm a bit set in my ways, but to me it's like a spoilt child: it takes much more than it gives. And that opinion appears not to be limited to just the older controllers.
But to answer your original question, without the writing tool, controllers would be far more limited in the way the system presents information, and I think it would actually be verging on "unacceptable risk" to use this system without one.