I have a simple Suite project which installs two MSIs. When testing it the 2nd MSI failed to install because I forgot to rebuild it after making a change and the suite install caught the error and quit as expected. However the first MSI is still installed even though the 2nd one failed to install and the suite install as a whole failed. I've looked through everything and am not seeing anything I can set which will make it rollback the first MSI if the second fails.
I think you have to set it up as a transactional setup. Make sure that Windows Installer 4.5 is installed and group all the MSI packages that should be installed as a single transaction. I am working on this now but have not tested the theory yet. 🙂