I see. Yeah, I haven't researched them in a while since I was in the market for it. As for getting the discounts, I'd suggest signing up for their mailing list and "liking" their facebook page. It really helps when they send/post the discounts. Also, a quick google search might bring any current ones up if there are any. And, no. The IS does not come with a screen protector. Just top, bottom, palm rest, and trackpad.
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Also, just to throw this out there, the aluminum macs are very durable machines. I would say probably a very large amount of people that own them use them without any kind of skin or case. Is there any specific thing you're going to be doing with your computer that you might find a case necessary? If it's sitting on your desk or bed you really don't need much of anything.