1. The default Debian OS load I specified, had their custom /etc/apt/sources.list. So when I spec'ed Debian 5 (for compatiblity with specific stuff I had to run), then ran "apt-get update && apt-get upgrade" -- it automatically upgraded everything to Debian 6. Not cool.
2. They buy bandwidth from cheaper providers like He.net, Cogent, and I think some other provider. They may not be as low-latency and as well-connected as you like.
I have servers in the NorthEast on Level3 - bandwidth between JoesDC and this location was unusable (under 1Mbps). However, I did open a ticket and gave them traceroutes, pings, etc. and a few days later it was fixed, I can now get over 30Mbps between the 2 locations.
But, you might never know what response times are for your clients, as you can't measure speed from their end.
The only thing I've ever found close to hetzner.de in the US with good customer feedback is (though there servers aren't that close): http://joesdatacenter.com/Dedicated_Servers.html