Great advert and hopefully it might save some lives.
Over the years that I have undergone first aid training I've lost count how many times they've messed around with the Breath/Compression ratios, lastest I was taught was check airway, check for breathing, check pulse, two breaths 30 compressions - repeat.
I suspect the removal of the breaths is also down to people being unwilling to place their mouths around an unknown persons mouth, particularly with the risk of communicable disease / vomit etc., people are probably more likely to do the compressions rather than doing nothing at all.
I like how they use "staying alive" to time the compressions, I use "Nelly the Elephant", which someone mentioned years ago, though I always sing it in my head since I doubt anyone watching a uniformed Police Officer doing CPR and singing would see the funny side of it.
As someone else has mentioned, quite rare to restart the Heart, best bet is a Defib unit.
I've done CPR a few times, it can be quite exhausting, but I've kept them breathing. It certainly isn't a waste of time - any chance preserving life no matter how small that chance is should be given.