While I don't have any customs to compare, my V6-S universals just came in and are pretty impressive. A very noticeabe improvement over the W4R, and even better than the SM64 in many ways. Plus I can share them with others!
The included tips were too small for a good seal so it took some fiddling to figure out of the tips I had that sealed well and were comfortable, which sounded the best.
Due to the triple bore design they are fairly wide in the nozzle and might not work for someone with narrow canals, though.