I just got 28.1ms IPv4 pinging between a server in the UK (i.e. a good connection) and Hetzner Germany. The timing within Hetzner's network is surprisingly varied, so pings to some of my servers are 27.1ms instead, and pings to some IPs on a server are lower by a few ms than other IPs on the same server.
I just tried IPv6 and got 23.0 to 23.3 ms, so that's a pleasant suprise. Last time I checked IPv6 was higher latency. Unfortunately I don't have IPv6 at my office or at home so it's not worth using for my work.
From both my office and home, pings to my Hetzner servers are 50 to 85ms. That's because of the slow links I have locally.
Those times are not huge but all the little latencies add up when doing things interactively, especially those that take multiple round trips. You probably wouldn't want to run a game server with those latencies.
I found remote editing files with Emacs Tramp particularly slow at that latency because it does too many unnecessary round trips. For remote compiles I have an SSH session open and use Git or rsync to transfer files to/from my laptop, but that's annoyingly slow as well. I still use Hetzner servers for development because the compute hardware is much better than anything for a comparable price in the UK, but I would probably switch to a UK-located version if Hetzner opened a data center in the UK with similar hardware and pricing - which seems unlikely!