I installed three rubber floormats in our garage back in 2005. We had just moved from Chicago to Florida and the home we purchased was a builder's model. The garage floor had an epoxy coat already applied, however the epoxy started to lift where the hot, rain-soaked tires rested.
The builder had the painter re-apply the epoxy, however it still continued to lift underneath the tires. At the time, I didn't know the proper prep procedures involved as I do now, or I would have fought to have the floor correctly prepped and repaired. With everything else going on with moving a family cross-country, I decided to just lay down some garage mats to solve the problem.
In answer to your question, the rubber mats did the job in terms of protecting the floor, however over time, they have become discolored and there are tire burn marks. Plus, with all the rain we get in Florida during the summer, the floormats get a layer of oily water that builds up underneath near the edges. It doesn't smell that good either. (Think of rubber garden hoses).
I am in the process of remodeling my garage with all new cabinets and once that it completed, I will be pulling the trigger on a new floor. I'm leaning towards the Racedeck Freeflow system, however I want to wait until all the heavy lifting work is completed and I finish the baseboard trim as the floor will be the last thing installed.
Below are a few pics of my 8 year-old ribbed rubber floor mats. If I were to do it again, I would suggest getting either gray or black to help hide the tire marks and I would choose a coin or diamond grid vs. ribbed as they are harder to sweep/clean.
I'm sort of scared to see what's under these mats when I remove them permanently to install my new floor. I expect a good floor cleaning will be needed.
Another thing is that the mats do tend to move over time so you will need to occassionaly adjust them. If you park your car and turn your steering wheel, the mats will also tend to curl up. I have the residential grade, however some of the heavier commerical-grade mats might work better for you.
Good luck.