I know that as a BT (uk) ISP customer mostly I can ping google.com and it returns in 6ms from a BT IP, which would indicate they're using GGC. Sometimes it resolves to a Google IP in 12 ms.
Last month however it started resolving all the way to Amsterdam and subsequently to the US with a corresponding increase in ping time. Was this their way of saving energy by shutting down DCs, or was it a bigger problem like capacity or an outage? Either way despite the latency issues the fact it always works in a plus for their infrastructure team.
The reasons why this happens are complex and difficult to debug. Please contact your ISP and ask them to pass the details of the problem on to us.
There are too many variables its hard to tell what exactly caused your issues.
But generally speaking GGC nodes are very reliable, their support is responsive and knows what they are doing very well and most importantly it saves us insane amount of money (cause BW is expensive here), and our users are getting better service.
We got ours delivered about 6 months ago. It usually works fine but once in a while google services will act up, but most of the time the issue is at ISP end because even the GGC nodes needs BW to pull non-cached content, but if your ISP is overselling BW it will really hamper the performance on the GGC nodes. The GGC nodes themselves have capacity limitation, our 3 nodes has a total capacity of 19gbps, I am guessing if we were to saturate that throughput then the services will be affected.