the OP isn't venting about the delay. the OP is venting about the lack of timely updates from UA which i empathize with him/her on. it's a huge issue that they need to get under wraps. there are many times (almost all the time) when it's abundantly clear a flight will not leave on time and .bomb, airport monitors, etc. all show it as on time.
it's ridiculous and needs to stop. honesty's the best policy is a saying for a reason. give the people the info and let them decide.
and none of this "crew/ac swaps happen all the time" bs that i know i will get in reply. happens at ORD/IAD/IAH/EWR. doesn't happen at PDX.