I use both LC10 as well as LC8.4 on my MBP 15. I use a Valeo11 (next week this will be an Aptus17).
Capturing tethered is no problem. For this I prefer 8.4 because it is a lot faster in showing the capture.
I have used batch processing from LC10 as well as the image processor in ACR, this is not a process to wait for. I normally leaf, get a cup of coffee (or 2) have a bite, read some newspapers.
About 100 images will take about 2 hours of processing (both in LC10 as well as in PSCS2, can't wait to get CS3) . The badge will contain, levels, curves, sharpening and saving in PSD/Tiff files. All processing is done on 16bit files. After this process I can handselect PSD files for further work.
I use a MBP15 2.0Ghz with 2Gb of memory and the 100Gb 7200Rpm drive.
Sometimes I do the postprocessing in Windows on the MBP this will go significantly faster. Cannot tell you how much faster because I basically never timed it that way.
Under normal circumstances this would be totally unacceptable but this way I don't mind that much.
Eventually I might just add either a MacPro or a Quad Amd just for batch processing but than I need to pump the files first over the network to that machine which also costs my time.