In addition, don't underestimate the value of noise reduction in post processing. You don't want to do it for every shot, but you're probably not going to make a 16x20 print of every shot, either. For those important ones, it can be extremely worthwhile to invest a half an hour in careful post processing to minimize the visual impact of noise. If one hasn't done this, it can be amazing just how much can be done. One of my friends showed me a print of a church that we had both visited recently (on separate trips). I was blown away that he'd gotten a shot that I had tried and failed - it was way too dark for my Fuji x10's tiny sensor. Then he told me that he'd shot it with his Canon G11 - at ISO 6400 or something like that! (He doesn't like to carry his 5DMkII on business trips either.) We went through the steps he did for the noise reduction and it was an eye opener. His original raw file was horribly noisy, but amazingly, the print was not bad. It wasn't equal to a D3s shot at ISO 200 on a tripod, but from the print I would never have guessed that it was the G11 at a ridiculous ISO.
Briefly some of the things I do now to make noise less problematic (and these apply regardless of sensor ability or really ISO level):
1) use edge masking (in LR, there are surely equivalents in other software) to avoid having the sharpening apply to the noise.
2) use larger radius for capture sharpening, again minimizing the sharpening of the noise
When combined with basic luminance noise reduction, the above cuts down on visible noise quite a bit.
If noise is still a problem, usually it's in featureless flat areas, such as sky or a wall. In those cases I'll usually selectively apply additional noise reduction in those areas. Sometimes this can be accomplished in Lightroom with an adjustment brush that has maximum NR and NO sharpening. But usually this is where I have to leave LR and head back to Photoshop layers. At that point the gloves come off and I have to select each type of area and dup it into a separate layer. Then I run Topaz DeNoise on that layer, optimizing the parameters for each layer separately. Usually the main subject has no additional NR, actually.
At the end, sometimes it helps to add a small bit of rough grain in LR - I found this counterintuitive but it does work in some cases. It doesn't reduce the noise, it just reduces the aftereffects of all of the processing. The visual result is better, though.
This takes me 15-30 minutes depending on how aggressive I get, and of course I only resort to this level of effort if I have a really noisy capture that is otherwise excellent and worthy of special treatment.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!