I did free flow tiles for my home in the Colorado high country. They were great for driving the car in with slush and snow and having it melt and drain away so you weren't walking on the wet. However, a lot of the dirt stayed on top of the tiles as it wouldn't drop through the openings. And there was a lot of dirt collected under the tile over the course of the winter. The only way to really clean underneath the tiles was to remove them, which was no small task.
Also, I made the mistake of putting some white tiles where the vehicle tires would go. After the first winter they got dirty and I was never able to get them clean again.