I hooked up one of these LCDs
and noticed that the backlight flickers a lot when powered by the 5V from the GPIO port. The backlight uses ~100mA and the RPi was using just ~200mA.
The flickering is most noticable while booting, and persisted even when I powered the RPi from my bench supply.
Investigating further I unplugged the LCD and upon rebooting, noticed that the flickering also can be observed on the red power LED on the RPi.
The power LED is just connected by a resistor across the power supply, so this flickering represents glitches in the power supply.
Perhaps someone can catch the glitches on a DSO and post them up here.
Is it a good idea to add some extra capacitors? What type/value and where should they go?