Extra traction in adverse conditions for cross is never a bad thing, and certainly not at this price. They seemed a bit long, but even with small shoes on concrete they scrape just a tiny bit (clearly shoe model dependent though). Potentially the most cost effective upgrade in cross.
I recently purchased Specialized Moto Diva (Mountain Bike) shoes and they did not come with toe spikes. These toe spikes fit perfectly and they worked great during this past cyclocross season. They are much lighter than the pair on my previous Louis Garneau shoes. I even recommended to a friend who was looking for a back up set of toe spikes.
Whether you really think you are going to need the extra traction during a cyclocross race or the hard nasty winter conditions, you really want to just get them. The screws that they will replace a easily damaged and a pain to get out once they are. This is cheap insurance when you need to replace the foot bed or finally do want to take that screw out without stabbing yourself or damaging the shoe.
I mean, they're toe spikes. I'm not sure sidi toe spikes are categorically better than any others, but tow spikes as a category? Oh man. I had no idea how awesomely useful they'd be for cross.
These are some of the better toe spikes on the market. They are longer and thinner so dig right in so you can fly over barriers and up steep climbs in cross races. Most other soccer style cleats are to fat to really dig in. They are a must for cross racers.