Pros: These bushings will improve almost all stock skateboard trucks.
Like many other skaters have said, it's amazing what a difference bushings can make. If you are heavier like me, the Indy trucks I like are useless giving way to popping out bushings and wheel bite.
Enter Doh-Doh for my beloved Indys:
I fixed my cheap feeling Independent Koston pro model skateboard truck bearings with some slightly harder Doh Doh "red" bushings and now I rarely get wheel bite. Some riders like fancier trucks like Tensors or Thunders which have more graphics, more industrial designs with different geometries, and different weights.
Doh Dohs for my Thunder trucks:
When I first wanted to avoid wobble at high speeds when I first started out, I put harder Doh Dohs in my Thunder trucks and it made this truck very stable for fast straight runs. The Thunder trucks, unlike lighter Indys, tend to be heavy, so a heavy truck with stiff bushings work well for a very aggressive linear approach to skating ala Rodney Mullen or Daewon Song.
Doh Dohs for my Tensor trucks:
Sometimes, however, a very expensive specialized truck like my pro model Tensor Rodney Mullen trucks can have bushings that are too hard and only work with a very precise rider like the great Rodney Mullen. Since I am not a king at clean flip tricks on boards with stiff bushings, I took out the hard Tensor bushings and put in some medium Doh Dohs and these trucks, as light as my Indy Stage 9 trucks, still retained their manual technical feel but with more forgiveness.
Finding the right bushing:
Bushings can be used for transition park skating where soft Doh Dohs do the job, or can be an all around medium bushing like the ones reviewed here and replace gushy bushings as found on Indys or stiff as concrete bushings as found on Tensor Mullens, and can be found in hard settings to make a board avoid speed wobble.
One bushing is not good for one rider to work all forms of skateboarding from transition, to technical, to downhill, but Doh Doh mediums are a great start to feel your way around replacement bushings. If these don't do it, Doh Doh also have very, very soft bushings all the way up to rock hard bushings. Sometimes I combine different durometer bushings on the same truck to customize my ride even more.