Well my lead arrived today from the far east, so after a quick solder job I've been outside for an hour playing around (I did back up every module possible beforehand!)
First off, I've read and cleared all fault codes from every module - most of them were reporting some kind of error code - and for most modules, they have stayed cleared (though I haven't actually driven the car anywhere as not insured at mo). Now onto the fun/useful stuff!
I'd replaced the fan motor brushes this weekend so it was good to test all three speeds were working correctly. I also managed to turn off the automatic HRW <10degC function, which was great (T4 can't do that), and I think I've disabled auto door locking too but I'll need to drive it to test. I've also played with several settings in the LSM - including the fun police lights and wierd double-flash hazards, though I did think I'd caused a problem enabling dim front indicators and found that rather than alter their brightness, it killed the front sidelamps stone dead and even disabling the option or ign off/on didn't get them working again
Thankfully restoring the backup I'd made earlier did correct the issue. I also toyed with the 30% main beam as DRL but in the end decided original was fine for me.
For those still undecided, I'd conclude TOAF is well worth the small cost of a lead from ebay, and used purely for reading/clearing fault codes is safe for all. The coding options do need to be used with care, and backups are strongly recommended before changing anything, but this would apply to T4 and any other system which allows config changes to be made so is not unique to TOAF.