Rowan: Did I know you rode fixed on PBP 2007? My best guess at the time was that maybe 20-30 people did...
TCRoadie: Oh goodness, I just googled the frame you mentioned. All of the images show huge amounts of drop between the saddle and the handlebars, for starters. Out of curiosity, did you test ride one before buying it? It's possible that it won't be a problem (for example, if you have very long arms, or are exceptionally flexible, or if you have a very long torso and short legs so that you cut the seat mast fairly low) but it looks like it could be challenging to get the handlebars high enough in relation to the saddle to be remotely comfortable even over short distances for most riders.
That's not to say that handlebars shouldn't or can't be lower than saddles. But that frame is designed for a fairly extreme drop, which makes you aerodynamic for racing but will do a number on your back and neck fairly quickly if you haven't trained for it and possibly even if you have.
Another possible issue (and I don't know how to put this delicately, so I apologize) is that with a position like that, even super-skinny riders' knees are practically hitting their chests when they pedal if they are riding in the drops. If you have more bulk in front than a skinsuit, the problem is worse. I have seen some heavier riders with bars too low who end up pedaling with their knees sticking way out at the top of the pedal stroke in order to clear their torsos... which means that they can end up with knee issues because their knees don't have room to track straight up and down.
You actually didn't say what kind of "endurance" riding you were interested in, although you mentioned the Pacific Coast hwy, we just all jumped to the conclusion that you meant brevets. But you won't see many riders on any even that is called an endurance event with that kind of geometry except maybe some on a 12 or 24 hour race (and even then, it would be the exception not the rule). You won't even see that many bikes like that on most shorter regular weekend club rides. You see them at crits, time trials, and triathlons, but even a lot (most?) of riders who race on them do most of their training on other bikes.
I'm not trying to diss your bike, or tell you you have to go get another one. But it is something to think about. My own opinion is that the fit, contact points, etc, outweigh everything else, including gearing. And you can expect some of those preferences and requirements to change as you ride more, adapt to the bike, lose weight, find out what kind of riding you're doing the most of, discover new kinds of riding, etc. It's possible that everything will work out fine, and you will turn out to love the bike; but if you don't, it's not a model that is very forgiving in terms of making modifications.