Internet Explorer is the proprietary product of Microsoft and getting it to work in Linux and Mac can be a hassle. It is not that I care or love IE, but the fact that every time I designed a Web site or WordPress theme that looks great in Firefox, Safari and Opera, I can be pretty sure that it will look awful in IE, with all the alignment gone. As far as I know, IE is well-known to break stuffs. For that reason, it is necessary for me (and any non-Windows developers) to install IE on my Linux and Mac machine.
For Linux, I used ies4Linux, and luckily enough, there is also an ies4OSX for Mac OSX.
In case you are remote to X11 and darwine and start to think that there is a lot of command line interface involved, then you are wrong. There is no need for any command line at all. As the same as other Mac app, you simply double click to install and it will even create a desktop shortcut for you. If only installing IEs on Linux can be as easy.
The rendering engine in ies4OSX is the exact copy as what you see in Windows, but don’t expect it to be as polish as Safari or Firefox.
Don’t expect IE on Mac to run as fast as your Safari or Firefox. It is not supposed to be used for Web surfing in the first place. But if you’re a developer that wants to test your works in an IE environment, then ies4OSX is the right tool for you.