The light intensity is seriously lacking on the samples I've tried at the hardware store. Also, it takes a long time for the light to build up a charge, and then the energy that is stored is drained quickly.

OTOH, if you want a portable light source that you can lug around anywhere, I'd suggest an Inova microlight, which runs on lithium button batteries. These batteries have a longer storage life than your typical AA dry cell, and you can even keep the light permanently on your keychain. Sa light output pa lang, talo na ng microlight yung "Forever Flashlight" na yan. The initial expense is well worth the convenience and utility of these tiny lights.