What should I say -- they were roughly on time (apart from that ugly two hour delay in Frankfurt), and (as usual) more organized than KLM and NWA, but I'm far less satisfied than I have been with Lufthansa flights to other destinations in the past.
Annoyances started with the fact that Lufthansa is operating its US flights from a part of Frankfurt Airport which is accessible to transferring passengers from incoming flights. So, once you get close to your gate (way past passport control and usual security checkpoints), you have to go through another security control: A "routine" pat-down search, since they just don't have the usual metal detector gates there. Queues before this security checkpoint at times counted some 200 people waiting. Once through this check, there were close to no eating or shopping opportunities.
On the flight itself, service was rather slow. On the daytime flight to Boston, the annoying part was sitting in front of that empty tray for half an hour; on the flight back, the annoying part was that they would keep Economy class passengers awake for more than half of the flight. The meal served on the flight back was a little problematic as well: First, garlic was one of the main vegetables; second, they were serving joghurt pre-packaged at normal air pressure -- you can probably imagine the effect of opening this on an airplane.
Finally, mileage: Lufthansa has reduced the number of miles they give on Economy class tickets significantly; I'm getting some 1800 miles for each trans-atlantic segment. In practical terms, this means that frequent flier benefits and upgrades have moved far enough away to make the Miles & More program mostly uninteresting -- unlike KLM's Flying Dutchman, where benefits are granted at lower mileage, and reasonable mileage is granted for Economy class flights.
For the moment, I find myself not having a preferred airline any more. Probably, I'll try Swiss next.
(On the positive side, I should add that the classical music audio program was, unlike the movies, exquisite, including a rare recording of a Schumann symphony with Furtwängler conducting the Berlin Philharmonic Orchestra; also, the service provided in Frankfurt to a colleague who sits in a wheelchair was stellar.)