Cases are no problem, just make sure it has all the internals you may need, sometimes cases will use proprietary plastic rails for drives or things that you can't get later or cost ungodly amounts from the manufacturer
I would worry about scratches or dents on a refurbished case. I am not sure what Cooler Master see's as reasonable for there refurbished products. Since the case is the first thing everyone will see but I guess it also depends on how much they are taking off of the price for a refurbished product.
Well, depends on who's doing the refurb. The only three parts I wouldn't ever consider buying used / refurb are the motherboard, PSU, and case... but if it's a reputable seller like newegg, well... if you absolutely need to fit to a budget, go with it. If not, you're guaranteed everything you need with a new case - a refurb might not have anything but the case.
In general case refurb is fine, pay attention to the details of the case such as scratches or dents that would point to a compromise in the quality. Normally though the refurb will be on par or sometimes (if you're lucky) better. It really depends on who is doing the refurb though, look into reviews of that retailer etc.
EDIT: I clicked the link it says the product is currently unavailable....
Go for it, the case is not a bad case, and there should be some form of return policy if the product is damaged. $40 is a fine price, for a decent case that looks pretty cool I would take it if I needed one.