Our installer is written with Inno Setup and we are actually quite happy with it. Yet some customers keep asking for an MSI installer which they could more easily distribute
Wrapping an Inno Setup in an MSI package is not a trivial task. However, it is possible. There are lots of free tools out there that can be used to do this. You should choose one that also supports uninstall(s) and upgrades.
I have found only one free tool that supports upgrades and uninstall. Check out http://www.exemsi.com/inno-setup-and-msi