I'm surprised to hear this coming from Etsy, a place I thought of as doing deployment right.
All these things should be simple. You already have (or should have) a unified system for dealing with logging/monitoring/graphing/init scripts/backup across multiple services that are far more different from each other than they are from mongodb (Sharding strategy and slow queries are probably an application-level concern). It shouldn't be hard - in fact it should be trivial - to add one more service. At last.fm (disclaimer: my experience was brief and getting on for two years ago) it felt like we were running every database under the sun, but we had a unified system for doing deployment/monitoring/everything, so it was no bother to add one more if an application wanted it.