Bearing steel is generally good quality, high-carbon, chrome steel. It will get very hard, and is highly wear resistant. It's probably better than what was used in the "good old days" before the invention of high speed steel. In order to use it though, you are going to have to cut down the speed to about 1/3 of what you would use with HSS.
Basically HSS was created to improve machining rates. The addition of tungsten (the first HSS was based on tungsten), increases the hardening and temperature of steel, as well as the "hot strength" (IE, the strength when hot). This lets you run much faster without loosing temper, which is the main issue you will have running carbon steel at HSS speeds.
Tungsten Carbide of course is much more resistant to heat than HSS, so you can go much faster (IE, make more $$$ if you are in a production environment).
I would also recommend picking up some HSS blanks, they are fairly cheap. If you still want to experiment with that bearing steel, you may be able to find more information on hardening/tempering it. If you are just trying to save some money, you can get HSS blanks for a couple dollars, so you may want to look for other places to safe a few.
