I'm curious to know where, upon walking through your own front door during the slushy months, you put your wet boots. I can't imagine that you keep a rubber mat from the hardware store in your vestibule, but what are the options?
I would never keep a rubber mat from the hardware store in my foyer. The foyer forms a guest's first impression and you'll never get a second chance to put your best foot forward. The rule is that the mat should be large enough to accommodate footwear but nice enough to hold its own among the rest of your indoor decor. Plus it should not get caught in the swing of the door.
I have a silk Persian carpet and find that slush and footprints enrich the patina. Persian carpets were made with living in mind: The knots per square inch and the pattern help to hide daily dirt (though the rug should still be vacuumed on a regular basis). Other options include having extra door mats cut from the same material as your stair runner or other area carpets. Stone floors can even be left mat-less if you place a good rubber mat beneath the overhang at your front door for guests to wipe their boots on.
But when your guests come inside, what to do with their footwear? It's tough. I don't like a collection of dirty shoes in my foyer. You could politely give them plastic bags for them and put the bags in the front-hall closet. Better yet, why not, during bad weather, meet friends at a restaurant?