Just hope that the laptop manufacturers aren't greedy like the cell phone manufcaturers.
Many handsets use patented serial I/O between battery and phone. In theory, this lets it charge better since it can talk to sensors in the battery. In reality, it means that the phone can misbehave if you use a generic battery that doesn't have the patented I/O. Common "misbehavior" with generic batteries includes not charging the battery, not charging it fully, and depleting the battery as fast as possible.
No wonder OEM batteries "perform" better.
Greed, greed, greed, and patent lawyers are all you need sometimes...