^ UA and its personnel do sometimes mess up and have bad attitudes (as well as sometimes do and display the opposite), but I see little of that here. In fact, if I understand your post correctly, it sounds like you got lucky to be rebooked on your outbound; otherwise you'd have missed your return flight, in which case you really could have been SOL. Plus, despite the rerouting and lack of UA status, you were in E+ all the way.

I don't want to get into a UA versus CO thing here, especially since both airlines have their respective strengths and weaknesses. But if you'd been on CO you might not have fared any better under these circumstance and probably would have fared worse by virtue of the lack of E+ or even other premium seating when rebooked.

I think the lesson from this experience is these are the chances you take when you do such a quick turnaround MR.