Hmmm...This is tempting for me. I am wanting to buy my first mechanical keyboard, and was debating getting a WASD or starting out cheaper with something like this. Thoughts/opinions?
Go straight for the good stuff. You eventually will anyway. No reason to spend additional money on the stuff that is "meh" only to upgrade in a few weeks, right? 
From my understanding (granted I am still new at this), the Rosewill and WASD both are Costar boards. The only difference being the cable connection. Is that incorrect? Are there other differences that make the WASD board double the cost?
There are more differences between the two, mainly in the controller placement, etc. The WASD does not have a history of USB port trouble like the rosewill's do, though in my mind, fixing a USB port on a rosewill is not an "issue", just an excuse to solder more. One very excellent reason to go with WASD is they are an excellent company to deal with, and the person is really great. If issues/returns/RMA/etics/etc. are important, you really can't top WASD.
The best reason is, ofcourse, all the customization options.
So despite the additional expense (mainly due to lack of sales. I'd never buy a rosewill unless it were on sale) there are many good reasons to choose WASD over rosewill.
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Buying a rosewill for parts is a good idea, too. You get a plate (for a poker, etc.) and 104 good cherry keyswitches. You can't really go wrong there!