Hi Sushi,
I haven't actually gotten my HT1000, yet. Long story, but it should arrive next week or the week after.
For people with a 16:9 screen they can just leave the anamorphic lens on at all times. Then they would watch 4:3 material in the center of that screen just like with a 16:9 projector. The downside to this is that it takes about 30 seconds of pressing buttons in the menu to use 3D reform to get the 4:3 to fit right. Since NEC seems to understand that the anamorphic lenses are helping them sell a lot of these we're hoping that they will change the software so that we can then save this setting and get back to it easily. Some people are just programming their own remote controls to do all this, which is probably what I will do.
BTW: The 3D reform sounds like a great feature, since I think you can change the picture to fit your screen very well. There is also a feature to just turn lines off one at a time, which can also helping with lining up with the masking. By "off" I mean the mirrors trying not to project anything, not that anything physically goes over than line. One of the things I really like about using TheaterTek from my HTPC on my M20 D-ILA is that I can stretch or squish the movie in any direction to get it to line up with the screen masking, so I'm looking forward to having something similar in the HT1000.
Basically, for 16:9 and 2.35:1 material I think it is pretty easy. It sounds like you either just put the projector in 4:3 mode or do one other simple thing - there might even be an anamorphic lens setting. Those who actually have their projectors in their hands have pretty much indicated that it is very easy.
I may end up taking the anamorphic lens off at times for 4:3 IMAX films, since it is nice to make those big. For viewing with some lights on, I also might take it off for some other 4:3 material and put the projector closer to the screen and on a table when I want to get the extra brightness that using the full panel for 4:3 would give.
I've read here that the 16:9 images are about 14% brighter with the lens than without it. The extra pixels add some, but there is also some loss through the lens.
Sorry, that I couldn't tell you the exact setting.
--Darin