I bought the 123 Magic parenting book a few weeks ago as I was pretty much at the end of my tether with 3.5 yr old ds. I've been using the techniques for just over a week now (realised that I was doing so many things wrong after reading the book) and the turnaround in my ds has amazed me. I was so sceptical about it but I got Dh and my mum involved too and it's working an absolute treat. He's taken to it like a duck to water and has been the most amazing well behaved calm little boy all over Xmas. I'm now enjoying spending time with my little boy for the first time in weeks.
I'd be interested to hear of other success stories or otherwise and some tips to not let things slide (the main one I've had trouble with us keeping my gob shut!)