Key questions to ask are:
What are you trying to do? If simply hosting a website, there are other solutions to do this that are simpler and more cost effective. If you are using some vendor's application and needing to push it out via web/mobile, then Microsoft IIS is a great tool for the job.
What is the level of security needed? If just simple security, then there are other solutions to do this that are simpler and more cost effective. If more granular and complex security needs are at hand, then Microsoft IIS offers extensive security customization regarding access, accounts, ports, etc.
What type of administration and management are you looking to give? If you want a one time "set it and forget it" type environment, then Microsoft IIS can be it for you. Or if you have something that needs to be constantly changed and updated, Microsoft IIS also offers the flexibility and speed to keep your environment going in a fast paced businesses.