you are right - we are currently working to fix the problem in the delay service, it should be up soon.
the service doesn't show you the exact distance between 2 POPs - well, sometimes it does, if the have a measurement between them - but in most cases we approximate it based on more than 1 measurement between different pairs of IPs. We believe that our approximation is accurate enough in most cases, but sometimes it is not and also there are pairs of IPs (lets say 11-12% according to our testing) for which we fail to provide any approximation.
We'll appreciate if you could use it and let us know what you think about results you get, and hope it will be helpful for your research.
After we fix the bug of course