The technical help documentation could be improved. One of the biggest complaints within the GIS community is that, while they do have lots of documentation, it's a bit rubbish. Sometimes, we want answers we can't get, and it's on their software. Very often, you dig into something, but you don't get the answer. You get everything but the answer.

I think that the interface and the importing from external data sources and external databases should be simplified a little bit. The product originates from the engineering world and it is doing more to target business users now. I believe that the user interface and the integration of maps with the external databases could be easier for less technical users. There are other platforms that are doing this better than ESRI (Environmental Systems Research Institute) Maps for Office. Some products are more targeted towards business users. These models show that the integration of external databases with maps could be simplified more to appeal to those markets. This level of user-friendliness is the main thing that is required by business users.

For the desktop edition, ArcGIS is fairly resource heavy, this is to be expected when analysing large data files like shapefiles and vector data etc. So optimisation and fully using a computer resources is always an area to develop for the software.

ArcGIS Online - currently being developed to allow users to do previous computations online in a browser. Unfortunately not fully recreating the desktop version as it has fewer features and issues with computation failing means you have to reconfigure and restart the process i.e. you complete lots of form like information box and try to run a spatial computation and the browser freeze, all the entered information is lost and you have to redo it again. 

Maybe not resource heavy but resource dependent as a better term, it uses a lot of processing power in comparison to other software and simple basic applications like Excel. Often you can get limits to how much you can do with the software and it's a scaling issue as geodata sets for GIS works a lot with shapefiles which are the equivalent of millions of rows of points of data.

There is always need to improve how the software runs and make it faster and getting better machines to process it.

The management functionality along with management from applications outside of coverage are lacking.