HD-SDI ingest is only useful during live-recording over an SDI cable, reducing your mobility. Once it is recorded on SxS card, HD-SDI is not better than a plain copy to your hard disk.
Maybe I should formulate it differently, I believe I would be able to mount the deck on the camera, using a cheesy plate and be able to move. Then I would record through the sdi output and then plug the SSD in the computer. From there I was wondering if I would see a real difference with my .mxf files and if premiere would be happy manipulating 10bit uncompressed video. (with my computer specs)
You realize that uncompressed HD-SDI signals can take a bandwidth of up to 1.485 Gbps (4-4-4)? That in contrast to normal 35 Mbps from the EX. I don't know what signal comes out from the EX, but I think that it maxes out at 4-2-2, which reduces the required bandwidth substantially, and there are discussions about the location of the SDI chip in relation to the DSP in the processing stream. Sony has been rather unclear about that, but it heavily influences the quality of the signal over SDI. Before the DSP is great, after the DSP is makes no difference.
I wonder how many would see the difference on a plain clip, but if you are chroma keying, then it will be quite visible (assuming the SDI is located in front of the DSP). But it requires a hefty disk setup.
If you go for the HyperDeck Shuttle 2 (a later model than I have) not only can you record uncompressed 4:2:2 but you can go compressed ProRes or DNxHD MXF compressed 10-bit video files. To tell the truth I have not used it in any real shooting, so I cannot tell you if it is worthwhile. If you are on a PC you have to get a utility to allow you to format and read the Mac SSD disk drive..
And as Harm has said it requires a very hefty disk drive setup to play this successfully into Premiere. Also it requirs a very high write rate SSD, I have several early generation SSD's that do not work in it.