Not that I've experienced any specific issues, but I had some free time on my hands this evening and decided to setup SmokePing on our Linux broadband router (see signature). I have added
www.thinkbroadband.com and the site you mention (www.pown.it) into the configuration. The graphs effectively stat response time together with standard deviation (smoke) so lets see how this pans out.
If anyone wants any other sites added, drop me a private message. This is running on a 50Mb connection in London and the Linux box employs traffic shaping so that ping request packets originating only from the box itself will be sent out ahead of all other out going traffic (which means if someone is torrenting, it should favour smokeping's packets over theirs and so hopefully always guarantee the fastest possible delivery of the ICMP echo-request packet outbound, although, I can't control the inbound so much - but it would take quite a bit to saturate a 50Mb link).