I'm not sure why I'm replying to this, but here goes...
I certainly agree that Honda does indeed suck. At least, their technical knowledge of the cars they produce sure does. My own experiences have confirmed that many (most?) of the Honda techs I spoke with don't even have elementary knowledge of how a typical fuel injection system works, much less that of the Insight. However, I am very disappointed at the content of your website. It could have been a GREAT site, that covered the advantages/disadvantages and reality of owning an exotic and limited production car. But as it stands right now, it boils down to several pages of you complaining, giving 10%of the story (based on what I have read on this forum) and just being generally negative. In addition, the most important section of the site, the Tech section, doesn't exist! In my quick review, I saw no details on your conversations from Honda, no dealership experiences, nothing.
Wait...I took another look at the site and the paragraph above isn't exactly accurate. Due to the design of the site, the scroll bar was hidden about 200 pixels off to the side of my browser. Maximizing the window and doing some horizontal scrolling found it. That said, after a quick read I still get the impressions I stated above. Little technical detail, many inaccuracies. For example, you mention an IMAP sensor...IMAP is an acronym for Internet Message Access Protocol. It is the replacement for the venerable POP protocol. What you probably meant was MAP sensor, standing for Manifold Absolute Pressure sensor. I believe that I have already corrected you previously regarding this sensor on this forum.
I also noticed that you centered on the O2 sensor incident. It is COMPLETELY normal for ANYTHING to do with exhaust work to be a major pain in the butt. Due to the heat, moisture and corrosive gasses, things like O2 sensors seize in place and often have to be extracted using extraordinary means.
Enough about the website. In general, your attitude on this site has been nothing but negative. Remember the 100 MPG thread in which you basically called everyone a lier since your personal experience did not agree? Just one of many examples.
Now, as I have said before, Honda dealers should not even be trusted to change oil. My first hand and very painful 5 month experience of dealing with Honda has been posted before, so I'm not going into to it. You know what? I stopped taking my car to the dealer and fixed it myself. Problem solved. Have you considered an independent mechanic? Or perhaps finding another knowledgeable owner with a service manual? Maybe learning a little about the basics of how the car operates? Either way, there is no reason to take the car to a Honda dealer at all. Especially when the warranty is up.
I'm really not sure where I'm going with this. It seems to be in all different directions...
Regarding coming to terms with the reality of this car. I did plenty of research before purchase, but it was not until my problem that it actually hit me. So what? It's basically an exotic car. Do you really expect dealer support? Perhaps you should take an RX-7 to a Mazda dealer, and then you will discover how abysmal support truly is (not that I have ever done this). I think it is UNREALISTIC to buy a 1st run car with a powertrain that is new and immature and then expect it to be as reliable and cheap as a CIVIC. Clearly, the Insight is not a car for you. Perhaps you should sell it, take the loss, consider it a learning experience and go buy a used Civic?
Now, for the technical stuff. If you have killed yet another cat, then there is obviously something horribly wrong. The troubleshooting steps are the same for ANY car at this point. Verify:
1. Fuel pressure
2. Ignition (this will light a CEL for sure)
3. Intake air temp, coolant temp (will cause the ECM to run the car rich)
4. Have injectors removed and ultrasonically cleaned
Like any modern car, the Insight's fuel system is computer controller. The ECM relies on multiple inputs (most important being the temp sensors, LAF sensor and MAP sensor) to determine a fuel curve. If any of these sensors are slightly off, bad things happen and a CEL may not light. The factory service manual contains procedures to check these sensors, which any mechanic can carry out.
Since there's no way you spend time in lean burn with your current lifetime mileage, you are not burning them out but poisoning them with fuel. Are you perhaps burning kerosene instead of gas? Regular 87 octane will do just fine.