The noise is moderate, no worse than the TSDZ2. Noticable, but okay and within expectations. Build quality is night and day compared to the TSDZ2 (I run the OSF versions). The X1 just feels like a much better quality product overall. I'm aware of the cooling mods with the TSDZ2... I just never found the time to go that route and then the X1 showed up. Power on the X1 is amazing by comparison, so much so that I need to do some tuning to make sure it doesn't eat the small cogs on my brand new 10-52T cassette. It seems to keep a fair bit of torque applied when shifting, even when I back off during shifts... I'm hoping a simple timing fix in software will solve that. Otherwise, it's been very promising given the 15 minutes of ride time I've had on it so far. Mechanically, everything is perfect, I now just need to make some fine adjustments in software.
PS - in many ways the X1 feels a lot like the OEM motor Rocky Mountain uses, and has a similar noise level. Not as refined as the other OEM motors, but certainly decent.