I have had my morphia case for just a couple of weeks and it has operated fine..... I did what they suggested and switched to the case when my battery indicator reached 20% and my phone was then fully charged so the 80% additional capacity claimed seems true.
The only fiddly issue, as reported elsewhere, is that a small extender may be needed in order to use the headphones socket. This is supplied.
I also found it a little scary when I first used the case as I couldn't see exactly how to separate the bottom part of the case and this requires a fair amount of force. However I persevered and managed to separate them and insert my phone ok - to some extent it is reassuring that the pieces fit together so tightly.
Please note also that with the case on you cannot connect your phone using the apple USB lead. The supplied Micro-USB is fine but only charges and does not sync. Thus to sync with the Morphie case you will need to sync via WiFi. Not a problem in my case but just something to be aware of.
Got mine in the post today I'll be testing it's extra juice capabilities throughout the day, the phone doesn't slip into the case because of curved bits of plastic attached to the bottom of the case so I needed to prise it in, after clipping on the battery bit I found the fit is nowhere near as snug to the phone as I thought, not completely dissatisfied but could be a bit more polished for the price