
I've been on this game since January 2006. I have to say GW is a great game, but since 7 or 8 months ago, I've being experience and horrible lag, rubber banding, network issue, constant gw.dat file corruption, fragmentation, ports, you name it, the thing is I can't play in peace.
I've tried all in my power, including contig.exe, constant client reinstall, port forwarding, connect direct to the modem, drivers update, modem reboots, and many other things, excluding contacting either my ISP or GW Support (back 6 months ago I spent days calling my ISP and finally I couldn't solve anything, ANET helps little, ISP blames ANET, ANET blames ISP).
Last Saturday and Sunday I lived moments of glory as I played normally, without lags, everything went back as it was until Monday. I can just play 4 hours / day as I get very busy all day, and I can't enjoy the game when I get home.
Some friends with same ISP doesn't have this issue, although have experienced it before, what is left to say? I hope GW2 works different, I simply hope it just work.
I jumped to WoW because of this, no lag at all, but got bored 2 months after and stop paying, and went back to GW.
In the mean time, I can only play other games I know, such as Gunbound, or just surfing the tube or Internet in general. My favourite game is unplayable.

EDIT: I forgot to say, that 3 months ago I built a new PC, main speks are Core 2 Quad, Radeon HD 3870, 4GB ram, 64-bits Windows Vista and 7,000RPM 250GB hard drive, and still have the same problem.