The "hood-mat" is (in most cases) used for fire suppression. If there is an engine fire, the heat melts the plastic tabs and the mat falls and smothers the fire.
The problem is that its UGLY.....and it collects and holds dirt.
I've done 2 things......
1. Take it off (carefully) and vacuum it. Replace it.
2. Take it off (carefully) and paint it with some latex fabric paint and a 3" roller. Replace it. It works great.
The other option is to leave it off. I've taken the pad off every car I've ever owned and never had an issue with the paint on the hood. Heat suppression is not the purpose of the mat anyway.
By taking it off, the underside of the hood becomes very easy to clean.
This pic was taken before I clear-coated under the hood......its much shinier now.....
As for the issue of fire.....I reallize there is a certain amount of risk with taking off the mat, from the standpoint of fire, and if I drove older cars, I wouldn't be as likely to take off the pad. Since my car only get about 2000 miles per year in mileage (2 miles round trip to work), and it's like brand new, I'm pretty safe.