That being said, I'm using Powershell + EPPlus + SQLPS to push data into a .xlsx file, and simply use SSIS as the process control layer. Seems to work OK for me.

Like others, the usual ways before EPPlus (and not being able to buy CozyRoc's custom controls or others) for getting data into and out of Excel via SSIS just seem...lacking, in my experience. the Excel Source and Destination data flow tasks work, barely. For some things, that's more than OK. Using a template spreadsheet file is...hacky.

Solutions that require Excel to be installed on the SSIS server work, but they're definitely not what Microsoft considers to be even good practice, as Excel isn't really developed to be a multi-user solution. So that leaves out some of the other options, such as Excel Automation thru its COM Objects, however you want to approach that. Plus, now you have Excel doing its usual data interpretations on any data being imported that may not end up as desired or expected (like, importing US SSNs or Zip codes properly). The ACE engine works too, sometimes good enough, sometimes not.

I could, but currently do not, want to write custom data flow controls (source & destination) using EPPlus, so kicking out to Powershell works good enough, plus gives me control of the output format styles, putting the output data into an Excel Table, etc. If I were contemplating that, I'd also seriously just contemplate trying to get work to buy the CozyRoc controls.

And there's more available to do through EPPlus, too...set up Pivot tables, set up many (but not all types of) charts, etc.