Hi Andrew,
Your numbers look suspiciously good
That works out to about 7 images per second. If these are 12 mpx nefs, and figuring 15MB average per NEF, then LR4 is reading NEFs at the rate of 105MB per second. A high end machine can only copy NEFs at that rate, much less render down the images for thumbnails, prep the metadata and write the DB records, plus whatever else it needs to do.
If the app is smart then it is not reading the entire NEF file, but just the embedded JPG. If that is the case then out of camera embedded JPGs are only around 1.5MB, but if they were edited by Capture NX then they are around 5MB. So there could be a big range there depending on how your process your NEFs and what percentage, etc. But in even in this case a rate of 435 NEF's per minute sounds rather fast, simply based on what I've seen with various apps I've tried. I have not demo'd LR4.
From a slightly different perspective, those 35,000 NEFs are probably very close to a half terabyte of data. I'd like to have amachine that could just duplicate that amount of data in 80 minutes, without doing any other processing
I don't like to disagree with someone when I have no experience with what they are talking about- just trying to say that the number raises some alarms. Is it possible that LR4 is only partially processing the images on the initial ingest and then finishes them in a background process that is not obvious?