I would just make sure that you can return the product if it doesn't work - call and ask someone at Newegg and inquire about the exact product if you want to be absolutely sure. If they won't let you make a return on an open-box item, then don't make the purchase (also check whether it will be at your cost to make the return). Either someone returned it because there was something they felt was "defective", (and Newegg missed the "defect" during inspection) or they used it shortly and changed their mind. If it was someone who just changed their mind, then you'll likely get a perfectly good product at a discount. This is why it's critical you check everything about the item when it arrives and decide whether it's at 100% before the return window passes. Always keep in mind that they are in the business of selling as many items as efficiently as possible, and that there are certain quality control issues that arise due to the volume of products they deal with.
Happy bargain hunting!