I believe you have a menu called Content (I'm on the Swedish version so the name may be slightly different, possibly View). From there, choose Default orientation , while marking the thumbnails you want to affect. Then they are most likely all displayed in landscape orientation.
DNG:s (or Tiffs, for that matter) are not rotated by Rotate Jpeg. And what you rotate with the small arrows left and right in the Information bar is only the view, the picture itself is not touched. Default orientation resets that view.
Mathias L

Now here's more:
When EM2 works as front application on JPEG Rotate it uses around 5 percent of the processor (setup: MB Pro, OSX 10.6.5). Cover up the main EM2 window with for example a Finder window, and the percentage increases to around 24, as does the speed. Cover up the progress bar too, and the percentage increases to 60-70, and now you're done!
If you hide EM2, the same thing happens. Since the EM2 won't take any commands while the rotating is in progress, you have to do it from another application ("Hide others") and if you want to observe the processor usage that has to be Activity Monitor.
Not practical for everyday work but it sure demonstrates the effect very clearly.
Ho, Apple, what's going on?
Mathias Luther

With Amadeus Pro you can mimimize the progress bar along with the file window, yes. That's when I noticed the phenomena. With EM2 just covering it up is enough. But that's of course not how it should be. I suspect that the problem is somewhere on the OS side. And yes, I always keep it updated.
Mathias Luther

What was your previous platform (hardware, OS) ?

The camera embeds the rotation at capture into the image unless you tell it not to. You can have EM ignore that information for jpegs by selecting the thumbnails and choosing View>Default orientation. If you then want to rotate the jpeg itself use Action > Rotate jpeg. That rotation will show up the same way in any application.

Which OS, version of EM ? Might help.

Some more findings:
- the problem actually occurs only if you have the EM2 window with the progress bar visible. If you cover it up after you've started the operation for example with a Finder window, EM2 actually works lightning fast. The speed increase while covering the window is very noticeable.
No explanation still.
I've noticed something similar with the app Amadeus Pro (audio) under both Leopard and Snow Leopard. With Amadeus the window with the progress bar needs to be minimized during work. It significantly speeds up for example encodings.

In PS Camera Raw settings there is a checkbox for Update embedded preview when you're opening DNG:s, and that does what you would want. But I don't know if there's a similar option in NX 2. Anyway it seems it should be in the app that's doing the editing, not EM which in this case is only reading.
Mathias

Done some more research. The Mac OS Activity Monitor shows that EM2 uses up to 60 % of the CPU for 17 threads while rotating images under Leopard, but only around 10 % of the CPU for 10 threads doing the same under Snow Leopard. Likewise the use of memory is much higher under Leopard.
This must be part of the answer, but what can you do about it?
Mathias L

Bumping the thread, yes... I actually timed my Macbook pro 2,26 GHz Intel core duo with Snow Leopard against my 5 yrs old iMac G5 (single core) with Leopard and - the G5 won. Leopard rotates JPEGs 50 percent faster than the Snow Leopard.
Now, why?

I digitized my collection of roughly 50 000 negatives and slides using a Minolta scanner (5400HS), Vuescan as driver and  iView Media/ Expression Media 1-2 as DAM.
Each link matters: The scanner should be able to do batch scans (you don't want to forward every single frame manually), the driver should be able to make a high quality scan directly because you cannot PP more than a fraction and it should have a sensible numbering system, finally the DAM should be able to embed keywords, batch rename, rotate JPEGs (not only the appearance) and move files between folders.
Expression Media has done very well for the money so far. There is a problem however with EM 2 in Snow Leopard that makes rotating JPEGs slow (about half speed). No other problem though.
Being able to embed the keywords and descriptions in the image files themselves is very essential since that makes it possible to switch to another cataloging solution later if need be, plus it keeps the words with the images at all times. Doing it without opening and re-saving the jpeg is necessary for image quality.
If Lightroom does it all it may be just as good.

Anyone else noticed that JPEG Rotate works much slower under Mac OS 10.6 (Snow Leopard) than under the previous systems up to 10.5?
Rotating takes approximately 2-4 times longer than before, if not more. Rotating some 100 jpegs, mostly 6Mb but some 10-14 and some 2 Mb, takes around 20 minutes on my dual core Macbook Pro.
To me this is a serious problem since I often work with photographed text which should be portrait-oriented (and not only look like it is).
 A year ago i actually downgraded my OS when I ran into this the first time (it had some other graphics bugs as well) but now it seems I can't put upgrading off any longer. I've waited for either Apple or Microsoft (or PhaseOne) to do something, but no one seems to have even noticed.
Or is there a known remedy?

Mathias L