Same issue here like most others. For me it started after the patch this week. Massive lag spikes which would often disconnect me from the game.
I actually just tried guesting on another server. Had no lag for around 15 minutes then transferred zone and bam the spikes are back.
Even tried a reinstall of the game from a fresh download just to ensure it was not a problem with the client.
Like many others here it I am from the UK using Virgin media (cable). Again no problems with the internet in general ( as mentioned before I downloaded a fresh GW2 client last night from the link on this site in around 90 mins).
Looking at other posts it seems to be a mainly UK problem (although strange how it seems to occurred with different time spans – mine as mentioned has only been for the last 2 days).