High mileage driving and hybrid

I think the HCH would be a good move. My HCH consistently achieves better MPG on highway driving than street driving. What your actual MPG will be depends, of course, on your driving style. If you could lower your commute speed to 60 to 65 MPH, my guess is overall MPG should be about 42MPG.
Will the HCH last 150K? I cannot say with certainty, but looking at Honda's track record leads me to believe it will. Consider a 2007 HCH, as dealers want to move inventory to make way for 08 inventory. Tax credit (if you qualify) is still available; credit is $2,100.

you know, I might have to disagree with you guys in one respect. The OP is driving 90 mph? I dont think you will get that great of a mpg, you will be constantly stressing the engine. Take a test drive and see what your FE is going 90 mph vs the regular civic with a lot more horses.

Let me support my rationale that a hybrid is still better, even for 90 mph driving than a non-hybrid (I admit that a diesel would also be good).
Todays hybrids have an Internal Combustion Engine (ICE) that is too weak to provide satisfactory acceleration when compared to other cars sold in the US. I believe that it does, however, have sufficient power to do 90 mph in straight and level driving (I won't admit to any first hand knowledge of this fact :-)) and it will still get better mpg than a comparable non-hybrid car with only a larger ICE.
I agree with AirplanePilot that, a hybrid is best in stop and go driving, however, it is still better on the highway than the pure ICE with the same engine. They don't sell pure ICE cars in the US with anemic engines as small as those in the hybrids but that's ok, you'd need the electric drive in order to get any kind of safe acceleration when you do need it.
I see nark's suggestion, however, I must disagree. An ICE is generally at its most efficient state when it is being driven hard, therefore, you'll see that a small ICE near its redline will get better mpg than a larger ICE at the same speed but not working so hard.
I should, however, add that constant driving at 90 mph would be much safer with high temperature/speed tires. I don't know what the ratings are for the OEM tires but I doubt they're rated for 90 mph continuously. If you're in a state where 90 mph driving is legal (or close to a legal 75 mph), I assume it's a western state where temperatures in the summer get very hot. This could be very important. You ABSOLUTELY don't want a blow-out at 90 mph.

Good points, but I disagree with MSantos. Yes, the HCH is better for highway driving, but then what's the point of the IMA system? In theory, the HCH's IMA recaptures energy otherwise lost during braking, and reapplies it during acceleration. Therefore, a smaller, more anemic, engine can be used (except for the HAH-joke).

On highway driving, however, once you get up to speed (accelerate), then the IMA system practically sits idle, unless you must slow down or speed up (to pass).

Personally, if Honda still made the Civic HX, I'd recommend that car to you easily.

I do agree with ex-EV1 driver, in that despite not using the IMA system to its potential, you will at least see a better fuel economy than no other non-hybrid/diesel car will match.

Whatever route you choose though, please make sure MPGs are near the top of your list in your next vehicle purchase.

Other than the lightweight and aerodynamic wheels, the HCH has been given several other low CoD tweaks, such as the underbody aero panels, the wheel well covers at all four wheels, and the rear spoiler. In total these tweaks formally place the HCH at .27.

The regular civic has a CoD of .31 (and worse depending on the wheel style and other body treatments), which is already very good when compared to most cars in its EPA class. For all it is worth, a Prius II sits at .26 and if memory serves me right the dearly departed Insight sat at .25.
So along with the Prius, the HCH undoubtedly one of the most aerodynamic vehicles most people can buy.

Cheers;

MSantos