In response to this complaint, besides numerous $25 coupons, I also got a $100 coupon and a nicely worded letter.
I arrived at San Francisco Airport (SFO) at 715a. My plane to Kona, Hawaii (for a conference) was leaving at 845a. There was a huge line for baggage check in, but since I wasn't in a hurry, I decided to wait instead of going up to the gate and trying to get through with my bag (which is usually possible and which I should've done). But the line moved really slowly and come 8:45a, I was asked by some of the moving United Airlines agents to go to another counter where flights that were about to take off were being processed. So far so good.
The agent in charge (I think her name was Michelle Edwards but I am not sure, her ID is 172238 AT F196F4 SFOCS) tried to find me, but couldn't. She tried a couple of variations and said I wasn't in the system and all this time she had a copy of my itinerary (along with the e-ticket number) in front of her. So she told me to call my travel agent. I tried calling him, but it was Sunday and as I expected he wasn't in. So I went back to the agent next to her and he found me in a second! But then he called up the gate and told me that the plane had already left!
So I had missed my plane, thanks to a screwup by this agent. I think it's natural for people to make mistakes, but there's more: She admitted it was her fault and then said she'd fix it so I could get to Kaliua/Kona by the same day. She then checked my baggage and gave me a ticket to Kahului/Maui departing at 645p. Now, admittedly not being comfortably familiar with the Hawaii islands, and not having slept the entire previous night (working on a talk), I didn't realise that Kahului/Maui and Kaliua/Kona were on different islands, until I saw the departure listing that named the airports.
In addition, the agent was extremely difficult about the whole situation. When I asked her for a manager to complain about this (it was her fault), she said "do you want your ticket or not?" In other words, she (at least implicitly) threatened me about reporting this incident. But I decided to not make a fuss until I got to Kona.
So I resigned myself to spending 9+ hours in the airport and got some work done. At about 4p, as I saw the departure screens, it dawned on me that Maui and Kona weren't the same! So I went to the United Airlines Customer Service and the agent heard my case, looked over my itinerary, looked at the time the Maui ticket was issued (9a), and said "this is disgusting!" It so happened that the plane to Kona didn't leave until 1020a!
So the Customer Service Agent (who was extremely helpful by the way) said the best thing he could do was give me a ticket for the next day. He said I couldn't retrieve my baggage but he would make sure it would either get re-routed to Kona instead of Maui or would be picked up from Maui and flown into Kona. I went home that day and the next day everything went really smoothly in terms of the flight. I was in Kona shortly after noon, but my baggage wasn't there! I went to the local Walmart so I could get some clothes for the next day (when my baggage was found and delivered).
So I've lost one day of rental car use (it was a weekly rate which worked out to $34/day), one night of hotel room ($150/day), and 24 hours of my time, and some items which I'd not have bought if it weren't for the fact that the airline lost my luggage. I have written to the United Airlines Customer Service department and I am waiting for their response in this regard. Up till now, I've always tried very hard to fly United even if prices were somewhat higher because of their service. I am hoping that my faith in their service will be redeemed.