There is no correctness limitation on using FoundationDB in multiple datacenters, and if you do most of your writes in a single datacenter while using the others for disaster recovery, the latency is honestly pretty good too (especially with some of the new 6.0 features).

EDIT: I was wondering why this conversation was giving me deja vu, and then I remembered that you and Dave discussed this in detail last month: https://news.ycombinator.com/item?id=18258805