|Cabinet scraper prepared with no burr. Notice how light the shavings are.|
The purpose of the scraper, once you've tuned it, is local clean up. They are great for getting at some of those spots of tearout that none of your planes seem to be able to handle. Another great thing is that you can run with or against the grain with them. I have a piece of curly maple that has a couple of really tough areas with serious grain reversal. It's much easier to scrape it in a couple directions than to move my planes around it. I've run into spots that even my 5", 55 degree smoother doesn't want to clean up, but the scraper seems to tame just fine. The final finish will not always be quite as smooth as a plane can achieve, but the tearout will be gone.
Hope this helps!