I had a pair of Yaktracks for a couple of winters, and they turned out not to be what I really wanted. They do work very well on packed snow and you can walk inside most places without having to take them off.
However, they work poorly on hard ice, which make them less than ideal for walking around town in the winter. The hard metal coil spring doesn't dig into the ice, so just slides almost as readily as a bare shoe. If the ice has some roughness, then they help more.
One problem that almost got me was unexpected. I was leaving work, so put them on my shoes in my office. The lack of spikes makes them OK for walking in the building when just going in and out. I stopped by the bathroom on the way out, which had a hard stone tiled floor. I slipped and almost cracked my head on a sink. The hard metal on the hard stone was about as slippery as the shoes would have been on bare ice, but I wasn't expecting it.
Eventually one of the spring wires broke, so that was the end of the Yaktracks. I haven't gotten any replacements, but winter is coming and it's nice to have something you can walk around with outside without having to worry about slipping on ice. I'll probably try something with small spikes next. That may mean I have to take them off when entering a building. I don't know if there is something that works on ice and doesn't hurt indoor floors. Probably not, so I guess I'll get to see how that tradeoff works. If they are easy to put on and take off in a few seconds, then it will probably work. If not, they'll probably be more trouble than they are worth.
I am eagerly looking at other answers for suggestions, although I am surprised others liked their Yaktracks better than I did.