I am considering of buying a Mac Mini with a 1TB Fusion Drive. However I will rarely use OSX (except for iPhone application development) and will mostly be running Windows 8 through Bootcamp. In this setup, is it worth for me to spend extra 250$ on the Fusion Drive?
My understanding is if you want to use Bootcamp, you'll have each drive formatted and available to the software as a two-drive system and not as a one drive - fused hybrid item.
Out of the box, the BootCamp software will see if you have a CoreStorage fusion drive and just put the Windows partition on the spinning HD. There, it won't even get to see the SSD nor likely any of the data that exists on a core storage volume (which is a mix of files stored on the SSD and on the HDD).
I'd still get the fusion drive since you can always experiment with the BootCamp default situation, experiment with virtualization, and decide to partition both drives to be stand-alone and run BootCamp to install Windows on the SSD itself. Worst case, you don't like the experience and take advantage of Apple's 14 day return policy to get a different Mac if you don't like your Mini once you've tried it for a week or so.
Here's what you'll likely see when you get your Mac. The SSD will be
In system profiler under storage, you'll see something similar to this: