The ease of use for our customers to set up their own VMs in AWS with custom AMIs (and not having have an expert available all day). It is also easy enough that anyone can do it without needing any special training! I wish there was more documentation about how things work under-the hood so we could troubleshoot issues ourselves if they arise but overall this has been very helpful as far backfilling instances goes when needed most - during production outages where some users are impacted by them while others aren't because other nodes were still running properly from before those failures occurred earlier today etcetera..