I'm reminded of installing one in our office in the late '90s (well, 2 Mbits over here, but same thing: importantly, no latency!) which my co-worker loved taking advantage of to pwn all the kids in Quake with their awful laggy dialup.I play on a T1, 1.5mbps shared down/up. No problems playing any PvE content or BGs but in huge Cyro keep fights I lag out hard.
That's the most frequent problem I've experienced, unfortunately. Occasionally it's at my end: once or twice it was due to my DSL being glitchy, another couple of times because Steam chose that moment to download something, but the vast majority of times the problem is evidently at their end and is resolved by quitting and restarting.... and hope for the best on ZOS' end.