Another recent option that came up is Pipelines as well. You can do a lot more with a Pipeline than you can with an Automation.
I have been playing with them myself for the same reasons. I have a lot of rules that happen on the form but I would rather have them just happen no matter how the user interacts with the record.
In your case it sounds like you might be able to get away with a formula checkbox though? What are the exact requirements you have? You mentioned that it needed to be checked when certain criteria was met based on selections in other fields, that sounds totally doable with a formula. If you post back I can help you with that.
