Top four reasons Windows wins and Linux loses
1. The Installed Base
2. PC Vendor Support
3. Hardware Vendor Support
4. Software Support
Source: Top four reasons Windows wins and Linux loses
To this list I would like to add:
5. Consistent Package Installation
In windows you have MSI files to install stuff with. They are simple to use and pretty much standard for every program I've installed.
In Linux I've used RPM's, APT and PORTAGE. Granted they are all easy to use it is still frustrating to me to have to know how to use all three. The less I have to think about something mundane (i.e. installing software) the better it is.
What would really rock Linux's world would be a single distribution system that would work with all distributions. That way the distributions could work on making their distro better and not have to worry about maintaining an Open Office or FireFox install.