About 300 miles so far, mostly commuting with a couple of 30 mile joy rides, there have been no more mechanical issues so I'll say a little about my ride impressions.
I'm a believer now in chromoly framesets reducing the jarring on rough roads. I don't know if it's low-grade 4130 or better grade, but it does feel different from aluminum. The bike doesn't magically float over rough spots, but it takes the edge off of sections which have literally shaken the keys out of my pockets on my aluminum road bike. After I wear these tires out and get some 28's or 32's I probably won't even be picking smooth lines any more.
I deliberately sized up the frame to 56cm for the longer head tube, envisioning the so-called "French Fit". More stretched out, bars almost up to the saddle, less nimble and more stable. And it does track straight by my standards; no-hands riding feels so natural that I stopped paying attention and almost bit the dust on a pot-hole.
With that setup and the weight (~30 pounds with all my accessories on it, plus 5-10 extra of me that doesn't need to be there) I didn't expect to be fast on it, and I was right about that. My commute now takes 30-35 minutes regardless of the regular route chosen and distance, whereas in the summer on my road bike it's 23-28 minutes (not including hammering or lolly-gagging). Don't even try to figure mph average speed from that because it doesn't mean anything, but commutes per hour speed is meaningful and is consistently around 20% slower. Counterbalanced by the fact that winter, rain and dark is always slower, but it's still a factor. For me, ten minutes plus or minus on basically a half hour commute isn't an issue, although I will still chase "rabbits" given the opportunity.
On my training ride this weekend I did drop a roadie on a long hill (that's an obligatory story for both commuting and fixed gear riders, right?). But the rest of the story is, it was only because I physically couldn't go any slower with that gearing and he was resting or something. 100 to 150 feet rise in a mile is pretty much my limit with this bike at the slowest possible speed, and it better not be more than a mile or two at that. I have ambitious aspirations to improve on that.
The unexpected gotcha of fixed gear by the way, should anyone want to jump in and try it commuting like I did, is when you've built up some speed going downhill and you've reached your rpm limit of keeping your feet on the pedals in any coordinated fashion. For me without retention that was around 140-150 cadence. So, obviously, you grab the brakes. The gotcha is that braking at that cadence feels totally different than smoothly spinning up to it, if you're not ready for it. So there are a couple of things to learn before barreling down a big hill. We're probably better off training up gradually than taking things to the limit right off the bat.