Someone willing to poach you from your current job- where they once worked (is it right to assume that they are now a competitor to your current job?) doesn't display much in the integrity department. What's to say he's not going to lay you off a few months down the line? If you're happy and have great retirement benefits, I'd politely decline. Then again, I think very highly of loyalty.
Depends on the industry and level of position I think. In my line of work, it's just a matter of where you fee like being shit on at the moment.