The only caution is this:

Seat assignments are not guaranteed. UA (and many of us on the board) will sympathize with your situation, but point out that your class-of-service is what they guarantee, not the specific seat. Therefore, I wouldn't center your email around the "I lost my seat" aspect, as you will get a form response from them.

The focus of your email (and the niggling problem, really) is the way in which your checkin and seating was handled. Why did UA release your seat? Why did you not get another E+ seat instead? Why were the agents so uncooperative?

I think you may have already emailed, but in the future, I'd focus on the *process* issues, and not do it via email (as that seems to rarely achieve significant results). Go ahead and give them a call if you'd like.

I wouldn't expect more than a CS25 or some miles, btw. Also, did you confirm whether the aircraft was swapped? Were you on the same plane that you had originally booked on?

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