I bought Bye Bye Standby primarily to enable me to switch my broadband router and modem on and off over night. Being in a slightly inaccessible location downstairs, I very rarely bothered to go and switch them off despite the fact that they were burning electricity round the clock. Buying the triple-pack allowed me to also control the computer, monitor and speakers, as well as my TV, set top box and aerial amplifier. Individually, few of these things were drawing much current, but by using a trailing socket and plugging in several devices, a worthwhile saving can be made. I still have to switch my speakers off the old-fashioned way because they make a loud noise when switched on and off at the mains. This can't really be blamed on BB Standby as it is beyond its control, but bear in mind that if you want to control speakers with it, that they won't quietly switch on or off.
The product itself is well made and easy to set up and use. The useful 'group' function allows my computer and router to be switched on together, but I can also switch the router off if I'm not using the Internet. As others have noted, it would be useful to have a switch on the plug unit itself for when the remote is not to hand, but otherwise the design is good and the units respond instantly and reliably to the remote, even through floors and walls. These units are for relatively low draw (4 amps, I think) so don't plug in too much stuff. A higher capacity unit is available from the same company.
The environmental credentials of the system seem to be somewhat overstated. The units are made in China and delivered in a tough plastic blister pack, a fact which is promoted as 'secure' on the company web site. This means as well as the carbon cost of manufacture and shipping half-way round the world, the packaging is so hard to recycle, it will inevitably end up buried somewhere. It's not as if they benefit from display packaging on Amazon anyway, a cardboard box would have been fine. The savings that the associated literature claim can be made seem optimistic, although they are apparently from an independent source. The battery in the remote is a CR2032 that is not rechargeable and there are no instructions on how to replace it (on the positive side the remote is small). The instructions even refer to CO2 as C02. The units reportedly draw 0.7 watts when in use (presumably round the clock) so you need to be sure that the items being switched are drawing somewhat more than that. I have a 10 year old Sony monitor which has a very good standby mode (it audibly clicks on and off just like the BBS units do), using the BBS with this as the only thing plugged in might prove to be more expensive than without due to both BBS and the monitor drawing electricity when the monitor was in use. Items like the router, modem and aerial amplifier were unquestionably wasting electricity round the clock - it's worth doing some calculations to see what can be saved before buying.
I've given four stars because essentially the product is pretty good, it's just not quite as green as it's cracked up to be.