They really should have just let sleeping dogs lie. In trying to capture the brilliance of the first one, they fail quite badly. There are some good bits, though. It's always worth it to watch Firth and Grant fight. And Jones' stint in the Thai prison is mildly amusing. But this movie takes way too long to get moving into any kind of plot and doesn't have the jokes to keep you interested until the plot does materialize.
Another problem is that they took two fairly major characters from the first movie (Jones' parents) and brought them back. But they did it in a badly diminished capacity. This wouldn't be so bad but there was really no reason to have them at all and their appearance seems superfluous.
Finally, Renee Zellwiger is never my favourite actress but she is downright difficult to watch in this. Everything seems awkward and wooden to the point that you want to ask her if she's in physical pain.
It really isn't worth a watch. Watching the first one again would be better entertainment. Don't bother seeing it.