Don't forget that you have to trade in your current phone to them. If you're okay with paying for half of your phone and giving it back, then it's an okay deal. If you're like me and buy/sell phones fairly often, it's not.
I bought a new in the box Sprint Note 3 a little over a year ago for $500 and just sold it for $300, so I "lost" $200. In your case you would have paid half of the $700 retail to JUMP, so you would have lost $350. Also, if they determine that there is any damage to your trade in phone, you will have to pay your $175 deductible to get it fixed before they will accept it.