I just bought two new Samsung Galaxy S4's and was initially pretty happy with the ability for full device encryption. Since it requires a 6 character alphanumeric password which also must become your unlock-pin, I'm less excited, since "unlocking your phone while driving" effectively becomes "texting while driving" and I don't wanna die.
My main question was how encrypting the device would impact utilization. I tried and failed to find benchmarks for this, so I decided to do my own. The only directory that I can write into, without rooting, seems to be /sdcard/, there is no sdcard in the device, so this is on-board memory. After running my tests, I question whether this folder actually gets encrypted.