The service might be of use but my concern is the latency. If I need to use the location variables (in my headline etc), they must be available to me ideally before the body starts. If they are doing a MaxMind lookup or any lookup of IP from a database, they are not serving cached content from a CDN and hence bound to have more latency then I expect from a library.

If my site is big enough with world wide visibility that it needs custom locations, it bet to be fast also