Windows Installer (MSI) files by compressing them and saving them in the same format. Two compression levels are available: fast and best. Best compression level is recommended, although it might take longer to complete. The compression process may require up to 384 MB physical memory for compression. We tested the application and out of a 5,763,072 bytes Windows Installer package resulted a 3,599,099 bytes file, that is 38% smaller. The configuration used: Intel P4 CPU at 3000 GHz with 1Gb DDRAM.
Pluses: MSI files can be compressed and reduced in size by 40%, something you cannot achieve using regular archiving applications (WinRar, WinZip, etc.),.
Drawbacks / flaws:
In conclusion: Fast, reliable and effective. Nice and smooth.