I bought the Nashbar one a few years ago and haven't used it yet.

Before I had it, I buffered the cups with blocks of wood and banged with a hammer. I know this is horrendous, but I swear, the results were perfectly fine.

It seems reasonable that unless you do this job frequently, it makes sense to have a bike shop press the cups in and press the crown race on. Last time I had a headset to install, I brought the frame and fork and headset to the shop. I broke my long-standing no-shop rule. No shame!