Mains sockets with USB charger

[ppppenguin]

Has anyone used mains sockets with an integral USB charger? Such as this, but many others available:

http://www.screwfix.com/p/product/1204F?mi_u=67274130&cm_mmc=Email-_-E16W01BE-_-Smallstickie3-_-1204F

Any thoughts on safety, reliability and standby power consumption?