When I was building the Shaker Trestle Table I espoused my love for the Lie-Nielsen #62 with a toothed blade. Well, Deneb Puchalski from Lie-Nielsen has put together a video demonstrating that very thing and doing so better than I could explain. The one thing missing from the video was a close-up of the surface after using the toothed blade. Fortunately I have one in my blog post. Hopefully this will help make things even clearer.
Although I have, and love, my Lie-Nielsen plane Veritas also makes a toothed blade for their bevel up planes as well. One difference between the manufacturers to consider if you are just starting your collection of planes: the Veritas bevel-up planes all use the same blade regardless of the length of the plane - smooth, jack or jointer. So, if you buy a toothed blade for your Veritas plane, you can use it in any of them. That may not be too much of a consideration because you really don't need the toothed blade in anyhting except for a Jack, however, being able to swap normal blades could come in very handy if you have different blades honed at different cutting angles (one of the key benefits of a bevel-up plane). This is a small point but if you're on the fence about which manufacturer to go with it may help your decision-making.
Incidently, you will only find the toothed blade available for bevel up planes. Here's why: the "teeth" are created on the blade by milling channels into the back side of the blade. If you were to mount that blade in a conventional bevel-down plane the channels would be facing up. The "shavings" from a toothed blade are very fine and granular and they would all get jammed into the channels under the chip-breaker and quickly clog the plane. On a bevel-down plane there is no chipbreaker and the milled grooves are on the bottom of the blade making for a nice smooth operation.