I looked into it with a buddy sometime back. There were mixed comments on Rimfire Central and other rimfire forums about improving accuracy. The comments about results from using the tool were pretty positive concerning expansion and penetration using the different rods and tip designs. The biggest repeated concern was trying to be consistent with your hits using a mallet to drive the rods into the tips of the bullets. Many of the folks said if accuracy improved at all, it did not improve enough to justify the time and effort of using the tool. From most of what I read, the general consensus was, if you are looking to improve accuracy, find a quality ammo that your firearm likes and use it. If you are looking for better expansion and penetration, then the tool is pretty good.
Since neither of us really hunted much with a 22 rimfire, we decided we didn't need another toy to play with. We did purchase a Hornady Rimfire Rim Thickness Gauge. It's not a perfect tool, but yes, it does make a difference in accuracy when you sort by rim thickness. Really good ammo, Eley, Wolf, Lapua, etc. has more consistent rim thicknesses already. The tool made a difference when gauging and sorting CCI Standard Velocity ammo.