You get great support (always had phone calls answered pretty much instantly and emails answered within a few minutes and all the techs I've dealt with knew what they were doing).
You can issue automated hardware resets and even get a remotely-controlled KVM attached to tweak the BIOS or regain access to your machine if you messed up the networking config (usually only takes a few minutes to get the KVM attached).
Orders for new hardware are also really fast - dealt with within the hour and often in under 15 minutes.
But there's no such thing as a free lunch. If you host at Hetnzer, you have to be aware of the reasons why they're so cheap, namely:
1) The servers are 100% unmanaged. They'll install new hardware for you if you ask them but everything else is up to you.
2) A lot of their hardware is desktop-grade, e.g. Intel Core i7 CPUs and non-ECC RAM. They do have some server-grade hardware in their high-end range however.
3) Their servers are in Germany. So you get quite a bit of latency if accessed from Asia or the West Coast of the US (see [2]).
4) They don't have any DDoS protection. In case of a DDoS, your server will get null-routed (but they tell you first). Again: 100% unmanaged. Up to you to deal with it. I've been lucky enough to not have to deal with a DDoS but my first port of call would probably be CloudFlare it it happened.
Provided that you're happy to do some sys admin, Hetzner is brilliant for a personal server, a CI server or even a prod server for a bootstrapped startup.
For literally next to nothing, you get a really powerful machine that will easily handle big traffic spikes without a breaking a sweat. And dedicated machine means that you get excellent and consistent CPU performance and disk I/O. If and when your startup takes off and you get funding, you can then choose between hiring a sys admin or moving to a more expensive host that offers a more managed setup.
[1] http://www.hetzner.de/en/hosting/produktmatrix/rootserver-pr...