I do the ice bath thing after marathons and I believe it reduces leg soreness over the next couple days -- just get a bag or two of ice, throw the ice in a tub and fill with enough water to totally submerge your legs. It can be a challenge getting in ... okay, it's *miserable* getting in and I probably say some unrepeatable things when I do it ... but it's not so bad. As with other icing I think you only need to do it for 10-12 minutes to get the benefits.
I don't bother with it for anything except for runs over 20 miles but I suspect it would be beneficial after just about any run. It's one of things like consuming cod liver oil -- anything that unpleasant *has* to be good for you, right?
Note: it's pretty funny if you travel to a marathon and stay in a hotel with lots of other marathoners... you'll see lots of them shuffling from their rooms to the hotel's ice machines, using the ice bucket to fill up the tub ... sometimes they are even still wearing the mylar blanket they got at the finish line.
Ahh, the glamour of marathoning....