You have read through
this right? Fantastic site for digital cameras.
Anyway, I would guess he's referring to the lowest ISO, not the
only ISO. The D40 can do ISO settings of 100, 200,400,800,1600, and 3200. Auto and manual settings. That's a fine range. My D70's lowest setting is only 200, which has caused me problems for brightly lit scenes if I want to do blurred motion photography (think bridal-veil effect on a nicely lit waterfall). Having ISO 100 is great, as it means less noise (imager noise), and more flexibility. Changing the ISO on a digital camera affects the gain on the imager. You can be pretty safe just setting this to Auto and letting the camera deal with it. Even if it bumps up the ISO too high, it's a lot easier to digitally fix a grainy picture than it is a blurry one.
The higher the ISO, the more sensitive it is to light, meaning you need less light take a picture. But the higher the sensitivity, the more noise in the photo. Hey, it's just like speakers!
In looking at the link provided, I now understand the limitations of the D40 a bit better. The only lenses that will autofocus are the more expensive, newer variety that have their own internal motors. For instance, I have Nikon's good old 70-300mm telephoto that's a decent standard lens and is pretty cheap at less than a couple hundred bucks. That lens won't autofocus with the D40/x. To get a 70-300mm autofocus, you have to spend $500 for the AF-S version. Now that's a *much* nicer lens anyway, so it's probably worth the $$$ anyhow.
And you're completely right about the flash sync speed. If you don't a lot of flash photography (I don't, hate it. Flash to me is like an equalizer on a stereo: it artificially colors the material), then it shouldn't matter. It would matter if you're trying to do higher-speed stop-motion flash photography. Flashes can be useful for stopping motion, and a high sync speed means the flash can 'keep up' with the camera to freeze the action more effectively. Nikon is pretty famous for their flash technology, and so I'm sure the D40x's flash technology is fine for just about any situation. DPReview doesn't mention it as a 'Con', and they are quite nit-picky some times, so flash sync is a non-issue (IMHO).
If you're going the D40 route, I'd do the lens shopping first and make sure that the lens(es) that fit your needs and budget will autofocus on the camera. If they do, then the D40x is a truly excellent choice.
But again, even if you do use older lenses on the D40x, manual focusing IS NOT the end of the world. None of Ansel Adam's cameras were auto anything!
