There are some great filmmaking forums out there, including the excellent dvinfo.net forum and also the VFX-slanted Creative Cow forums but you need to use common sense in deciphering posts. The ProRes codec family has been a fantastic addition to the Final Cut arsenal of tools to use when doing video editing on a NLE, but there seems to be wild misunderstanding about the value of using it, at least to my mind.

Some background on bit depth and codecs: most all prosumer cameras such as the Sony V1U which we used for two of our documentary productions record to tape in 8-bit format. This means that in addition to potential compression artifacts associated with squeezing so much data into such a small space, the component images of the video only support  256 gray levels. In comparison, 10-bit images support 1024 discrete levels of information and 16-bit images ~65K levels. HDV therefore has the effect of reducing the dynamic range in comparison to film capture; from a practical perspective it reduces dramatically the information you can extract from shadow and highlights when working with footage that has extremes of highlights and shadow. There are other problems also associated with HDV such as the 4:2:0 color space, that you butt your head up against when shooting green screen material (never ever have contrast enhancement switched on when shooting green screen footage!!!!).

When we first started using FCP a few years ago, which codec to use on the timeline for my 24P HDV footage was answered in several posts in the above forums: Apple Intermediate Codec (AIC) was recommended. At the time I thought it was overkill - the size of the converted files was about three times that of the native MPEG stream formatted M2T HDV files from the camera. In practice though, it's worked out OK, although my hard drive space requirements are astronomical (something like 10TB and counting). With Final Cut Studio 2 came the first release of ProRes codecs. These promised smaller file sizes for handling HD material whilst being 10-bit. The only reason I can see for using ProRes for 8-bit material such as HDV is when performing FX/compositing in post. The file size in my experience with ProRes 422 is that they are at least twice the size of AIC-formatted files. As for ProRes HQ, it won't even play in real time on our Mac Pro quad core without stuttering. Fortunately, there is ProRes LT (released with Final Cut Studio 3), which produces files just slightly larger than AIC, but has the advantages of a 10-bit codec. I can see no reason whatsoever for using ProRes 422 or (heaven forbid) ProRes HQ owith 8-bit footage for regular editing. None. Period. In fact, aside from using HDV on the final cut timeline, which I wouldn't recommend especially if using any kinds of VFX, AIC still holds a very useful place in the editor's toolbox. For example, rendering out clips that have filters applied to them is the bain of FCP users. With AIC, a clip that's been rendered out as AIC can be edited for length, without destroying the render. Because ProRes is temporally compressed, editing the length of a rendered clip on the timeline results in a re-render being required.

Just my 0.02c worth, but AIC still rocks, isn't a resource hog on the timeline and can speed editing tremendously. If you read some posts in forums, you see  folks advocating Apple retire it  in favor of ProRes - I really hope they don't.