The battery is fine. It is a good replacement battery that can save you allot of money in repairs.
However even when going through the battery replacement process step by step with an online help video there is a large amount of risk. There are several points where pressure in the wrong way will lead to a broken ipod nano. You do need to use pressure as well as the connections do not give way easily (certainly no where near as easily as the online videos led me to believe).
After going through the process I am adamant I will never go through it again. I will either sell my ipod as a dead battery ipod and buy a new mp3 player or send it to be fixed at considerable cost.