Fair criticisms! It's true if we'd used Mongo Atlas or something similar it would likely have been a different story - often the MongoDB support spent half the time on the phone trying to work out what version of mongo, opsmanager etc. we were running.

Re criticism of OpsManager - I think this is fair, given the sheer number of hoops we had to jump through to get a functioning OpsManager system running in AWS - no provided cloudformation, AMIs etc. £40,000 a year felt like a lot for a system that took 2 or more weeks of dev time to install/upgrade. The authentication schema thing was a bit of a pain as well, though we were going from a very nearly EOL version of Mongo (2.4 I think).