gui design - What are the drawbacks of designing a Windows application to look like a Mac application?

I'm working with a company whose product is a Microsoft Windows application.

As the UI/UX designer (and as a Mac user) I want to redesign the application so it is more visually appealing.

Are there any drawbacks of designing the application to look more like an OSX app?

Answer

You're introducing two big problems right off the bat; breaking conventions and clashing styles. Don't forget that Apple and Microsoft have released different interface guidelines for their respective platforms : Windows UX Guidelines and the OS X UX Guidelines.

Using conventions is important and helps users work in your app without thinking (Don't Make Me Think!). Breaking conventions is even worse, because users will be confused and might initiate actions that don't apply to the current context. Context is important in how we interact with things; I see Windows 7 and I interact with my desktop a bit differently than I do in OSX--I might even interact differently than I do with Windows XP.

By breaking conventions people might not be sure what context applies; if I have a Mac App in Windows does it act like a Mac app or like Windows? You're immediately bringing up questions.

Remember you want to take inspiration, not copy design. People like Mac apps because they're simple, they work without errors and they're visually pleasing. "Copying" those attributes is great and works on any platform. Copying the specific styles that work in OSX like the brushed steel interfaces and borderless windows will simply introduce clash in a windows environment.

Let's take iTunes as an example:

The main window just looks out of place, and the brushed steel OSX look is oddly mixed with the Windows Vista glass theme. Note the dialog box has to use the default Windows Vista styles as well.

Clash isn't always bad, but if you app simply looks like you copied a Mac OS app, it's not going to be visually pleasing and it's going to introduce confusion as you're breaking those Windows conventions.

Perhaps most importantly making your apps look good shouldn't be a platform specific task. You shouldn't be thinking "How can I make a Windows app look like a nice Mac app?" you should be thinking "How can I make a Windows app look nice, like a Mac app?"