There are really only two drawbacks to the Nyko
Charger Grip that I could see.
1) The earphones do not fit comfortably into their receptacle while the Charger Grip is in place. I discovered this after I had placed the Charger Grip on and went to insert my earphones. They simply won’t go. Now, you can remove the Charger Grip, plug in the earphones, and reattach the Charger Grip and with only very slight finagling, it will be fine. However, perhaps that may be taken into consideration for future designs. I never use my PSP without earphones and I am probably not the only one.
2) You cannot use your existing protective case with the Charger Grip, obviously. While the Charger Grip does offer some protection, it does not protect the all-too-delicate screen of the PSP, so I tended to pull out the Charger Grip, attach it, play what I wanted, then place the PSP back into the case and slide the Charger Grip back together to put it away.
Overall, the Nyko Charger Grip is a nice little piece of hardware. While it may not massively extend your battery life, it will greatly improve your comfort level if you already feel at home with a PS2 controller in your hand. At a price of $29.99, it may not be your cup of tea, but I know it really improved my PSP experience.