Tickrate doesnt tell anything alone, you should not care about the number.
Im sure battlenonsense makes video about it soon.
I realize it's not the end all be all, but having played many Source engine games it's been a fairly known constant. Ignoring interpolation/extrapolation issues (assuming a good connection), quick and dirty summary:
30 Hz and under - Bullet hits feel noticeably delayed. Shooting doesn't feel good.
60 Hz - Bullet hits feel near instant, however there is a bit of inconsistency in terms of registering hits
120 Hz - Flawless
It doesn't matter how good your engine's interp/exterp is, 20-30 Hz will never feel very good regardless of your connection quality. The delay for bullet registry is noticeable. As you get closer to 60 the delay starts to become less perceptible.
I'm not quite sure how the math works out when you combine input lag from the engine, network latency, and tick rate, but out of experience it's clear that tick rate has a noticeable impact on how good a game feels online. I've never played a shooter with a low tick rate that felt good.