Great little device that does what it says. I've used it for running multiple devices including the USB slot which I use to power a USB key MP3 player. I've not used the included velcro patch to attach it to anything yet, so don't know how strong that is.
The only minor negative, preventing 5 stars is that the space between the sockets isn't a lot and if the things being plugged in are wide, then they may not all fit in at the same time.
-- Update, 2 years later --
I managed to break it. My fault really, I tried to power a coolbox with it at the same time as charging my phone and powering the satnav. I didn't really count the amps, but it was enough to fry the innards of the plug before blowing the fuse. I guess it was a 5A fuse and I was trying to draw about 6. Oops.