This leads onto the question of compatibility between the various GIS solutions just mentioned. ArcGIS can open its native shape files (.shp), which is a format created by ESRI the developers of ArcGIS. Any map document files of type .mxd saved by ArcGIS are going to be in a format which will only be fully compatible with ESRI software. MapInfo can open files in the TAB format (.tab) as well as shape files (.shp) and QGIS can open both these formats. Opening these formats also depends on several other relevant files being present. However, a map file such as a .wor, .mxd or .qgs, can only be opened by the software which created it. So if you want to send a QGIS user maps in a MapInfo format you should send all the individual layers which make up the map rather that in a MapInfo workspace .wor format. Additionally, information about how those layers should display as well as projection information should be included.
Being able to read and write to files in various formats has always been a problem with software and it is not an issue which just relates to GIS solutions. With software upgrades it is often the case that even users of the same GIS solution can run into problems when one user is on a different version to another. Understanding that compatibility can be an issue means that extra care should be taken. This will ensure that when maps are being used between different GIS versions and solutions these compatibility problems are understood so that they do not become an issue.
If you would like to further explore how GIS could help your organisation jps services offers one and two day training courses in QGIS, ArcGIS and MapInfo.