I have 63 switches in my ihc.items file, and they are all using this feature. Besides that I have a few contacts and numbers, and they have mainly readonly definition. One number for the level in my ventilation system has ReadWrite definition.
The real use case is that this feature provide a very simple and reliable method of having correct status in openHAB regardless of whether a change was initiated by openHAB UI or a physical input push button attached to IHC. In openHAB it can be quite cumbersome to detect the origin of a change, and suppress additional activities if it was initiated by a physical button, because then everything is done. Before I discovered you smart binding options, I tried a variety of rules including wait, circular refences and sometimes also unintended endless loops inside openHAB. I wrote a posting about this, and it can be read on here (use Chrome to have English translation).
With this feature I can map my entire IHC installation quite simple without the need for rules. Rules are only needed, when I would like a special functionality. It is important for me that IHC is the master and holds all relevant logic and status. There are several reasons for this and one is that the installations in the house must always be working without being depending on 3rd party software such as openHAB.