We used it also. Ran into the issue that collection (?) names are limited to 64 chars(1) (which wasn't documented anywhere), triggering obscure errors while everything was fine from the Azure Frontend.

Also even simple queries using an index (and a uniform document structure) cost a comparatively huge amount of RUs compared to a competitor.

Icing on the cake was the non-support for paging at that time, and a total fuck-up when we tried a restore from backup operation (which can only be done by calling MS support, no automated way possible). If anyone wants to know details I can provide those.

Needless to say we switched to another provider.

(1) the names were generated by our automated deployment step, something like {environment}_{product}_{collection-name}