I was a little concerned about the success of this upgrade based on the comments here, but surprise, a complete success.
Firstly, I backed up the C and E partitions of my old drive (a reliable but noisy Seagate 500GB IDE) for later FTP'ing across, to preserve all my save games, dash settings etc. Well worth the effort.
I used one of the more likely converters (
http://mediagate.pbw...rter_Adapter_(1).jpg) after prepping the drive using XboxHDM. I was sure not to let the program set up an F or G drive as it doesn't allow for the larger cluster sizes needed.
After a flawless prep, I dropped the drive into the Xbox with the converter. To my complete amazement, it booted into UnleashX first time. And then I switched off and tried again, same result: booted right up, no error messages. FTP'ed a few files across, RARs, and was able to extract with no corruption, so I then booted the Ndure Toolset (usually found as Default.xbe in E:\NDTS), wiped the C and E partitions of the new drive and transferred my backups across. Once again, after a power on it booted right up, this time directly into XBMC with only a slightly longer delay; the splash screen showed for about a second more. Hardly a lot of lag!
Following advice about the tempremental nature of the XBPartitioner software, I first ran XBPartitioner 1.0 to build my extended partitions. Originally I wanted to have three seperate partitions - F, G and H each formatted with 32k clusters so as not to waste space - but this doesn't seem to be allowed for in any version of NKPatcher so I just chose two partitions, each 711.5 GB or 684.86 GB depending on how you group the bytes. You do this part in XBPartitioner 1.0 because there is a bug in 1.1 that hangs the console if you have partitions of over 1TB, even if it hasn't been allocated yet. When the formatting is done with 1.0, fire up 1.1 and press start to have the two new drives formatted with 64k clusters - this is ESSENTIAL, do NOT skip this step otherwise when you get past the 512 GB point you will start to have invisible data corruption, which could potentially ruin all those hours transferring media files across.
When this is done, you can boot back to the main dashboard. I used the In-Game Reset (Black, Back, Both Triggers all at once) to take me back to XBMC. This time it took about three or four seconds before I saw the splash screen, but it disappeared much more quickly, so not that much longer overall. I'm assuming this is because of the time it takes to read the partition table, which on a larger harddrive is bigger and therefore will take a little longer. For the extra capacity you get, it's worth it!
With all these checks done and no problems at any step, it was time to see if the case could be screwed shut without pushing the SATA to IDE converter out of shape. With a little gentle bending of the harddrive power molex, using the IDE cable clipped in place on the cradle to hold it down, I was able to get the case to snap shut as standard. After screwing it all back together, I plugged it in and was delighted to find it still worked, and that the CPU/GPU temps were lower, presumably because there's less heat in the case with this Samsung SATA drive.
FTP performance is standard; I'm using XBMC's built-in Filezilla, and transferring to it with the PC client version of the same. It averages ~5-15 MBPS, which is the same as the drive it replaced and the original 8GB Seagate that came stock with my Xbox. I've had the drive constantly being written to, transferring hundreds of MP3 files for the last couple of hours, and the temperature has yet to get above ~30ºc. In addition, the CPU temp is ~45ºc, the GPU is ~41ºc. - even with the fan on the lowest setting (2% in XBMC). Of course this is with the Xbox out in the open, sitting underneath the television - when I put it back under the bed with all the soundproofing it'll run a bit hotter, but either way this really helps the longevity of both the drive and the Xbox, which by now is eight years old.
Anyway, I'm happy to report that modern SATA drives can work very, very well in the old Xbox consoles if you choose a good one, and couple it with the right converter. Sure you still have the ATA33 bottleneck which increases the amount of time it takes to transfer files, and you are still bound by the 64 character limitation of the FATX filesystem (watch out for this when copying music files which don't have the track numbers at the start, for example!) but overall, this is a good solution for having a lot of standard definition content in one place. I have yet to watch it fail to boot!