Not had that long to road test this yet, but so far its working fine.
There are two minor issues, which I've knocked a star off for each... this is possibly a little harsh, but its more of a design flaw than anything else.:
1) You can only adjust one side, which makes the clip sit in a slightly odd position on your chest. Not a major problem, but would've been better to be able to centralise it.
2) The device uses popper-clips to attach both sides around the arm straps. This is fine for now, may not be long term secure. Again, its not a major issue but if you want this to last and take the strains of a heavy rucksack, its probably not ideal. This method of attaching also means, unless your straps have separated sections (fortunately mine does) there's no way of securing them in one place, and it'll therefore ride up the straps (presumably towards your neck!)
If I remember to update a few months down the line, I will to see how these two quibbles pan out... but for now its a reasonable price to pay, but the item description could do with more details like this in it!