I have been doing SFO-Europe in J for the last 5 years between 5 and 12x/year. By far the best is BA's latest flight out of SFO (currently leaving at 19:30), but you can't use your miles for it. As someone here posted, you can go to YVR on AS to pick up BA, but apparently it's no easy transfer and it doesn't work on the way back without overnighting in YVR; other Canadian cities are a one-stop flight on AA out of SFO.

Second best is LX's A340 via LAX. I'm absolutely amazed at how much better J class on an LX-operated AA codeshare flight on the A340 (not the A330) is than on an AA-metal flight.

The almost-flat almost-horizontal seats are definitely uncomparably better than the cr@ppy AA ones, and the 10+" screen video on demand / audio on demand system has lots and lots of great content (compare with small screen and 4 movies on a fixed cycle on AA, or the personal video), including cool live video from a camera mounted below the plane and one pointing ahead. Power is 115V AC and accepts both European and US plugs, making extra cables unnecessary. The air humidification system on the A340 truly makes a difference upon arrival and the day after, as 11 hours of ultra-dry air (typical of Boeing planes) is proven to make one groggy and real thirsty. Food (on white linens) and snack service is done 4 times on the ZRH-LAX flight (don't know about the other direction as I always sleep through), including freshly scooped Mövenpick ice cream in waffle cones, and water and drinks refill is constant. Premium luggage always gets delivered first (what a concept!)

Only downsides (all very minor ones): can't pre-reserve elite-reserved seats, their one-tray quick dinner does not have a warm entree, regular main meal service (on both directions) starts late and is slow, wines are unexciting, there's no quick breakfast option, and regular breakfast is served way too soon (2+ hours before touchdown) and is slow.

Incidentally, there's no bad seat on the 343 in J. If you're a window seat guy take note than in row 8 one of the windows "doesn't exist" due to wing structure going through the fuselage. Row 11 (I assume) is a bit noisier because it borders Y, but it gets food served first. From my searching FT in the past, rows 4 and 5 are the best if you like a quiet mini-cabin setting, but all the windows there (and most of the other seats there too) are blocked for STC elites. I have been unable to get LX to assign them to me even as a 5MM AA EXP, and the window seats there have always been taken by the time I got to the airport. Unlike with AA, there's no real comfort penalty for being in a bulkhead seat.

Oh, and *do* read the instructions in the magazine on how to best use the J seat: for example, if you sleep on your side, do not use the fully reclined position as it's not the most comfortable for that position!