Il s'agissait de

[Billy Bosworth]

I find the use of s'agir quite tantalising. I think I know what it means, but not well enough to use it myself. It seems to be a mix of "it is/it includes/it involves/it consists of...". 

The phrase that started me off was: Il s'agissait de trois pièces ... (describing a building layout). 

Would the man in the street use this construction? It is used more in the written word than spoken?

Are there instances when only s'agir will do?

[George Hunt]

Yes I think it is quite common and not really  just something you would find in use  as a written expression.

I like it a lot and  fined it a useful way of slowing down  the explanation. You can be thinking about what you are going to say  as you use it.

I think another similar phrase might be "il est question de....."

The task involves"  might be translated as "il s'agit de...."  but as you imply  ,it is a bit difficult to find an exact translation. You  may be right to be reluctant to use it yourself until you are familiar with it after finding it used in situations that make good sense to you. 

[Sandra]

Hi !

George is right (as always ;) ) but I want to add a small nuance :

"Il s'agit" tends to disappear in everyday speech, the man of the street as you say will prefer "c'est" or "il y a" depending on context.

But you will find a lot in literature, written language and official writings of course. :)

[Tux]

Ça ne se dit pas vraiment à l'oral surtout à l'imparfait, c'est plus du langage écrit.