Yeah, like I said, I've done extensive testing between BYPASS and DSP+DLY mode. That testing was all done without any other pedals in the chain, and done with the TF bypassed.
That being said, it appears the sole existence of the TF is creating a "hiss." Give it a try: run the TF alone, make sure the effect is off, then go into the pedal setup and switch between BYPASS and DSP (or DSP+DLY, makes no difference). DSP (aka the TF's buffer) gives a slight hiss. And like I said, it's not a big deal, as it's fairly quiet, but my concern is that the stacking of these pedals would also stack the noise. On the flip side (and I'm no science guy), maybe the buffer, changing the ohms from whatever they were to whatever they become, would make that noise the first time but not the second or third time. I don't know, and I'm not sure I even know what an ohm is! :p
Nevertheless, several reputable-sounding people use multiple xFactor pedals, and this doesn't seem to be a glaring issue people talk about, so I'm not worried.
I have not, however, tried the TF in the effect loop of my Alchemist. I'm afraid to, cause if I like it, I'll have to buy several feet of additional cable to reach my off-stage amp… Also, I have noticed no noise issues with any of my other pedals. I'm also not too thrilled about running my OD's after the delay…not quite the sound I'm going for. I will try it, though, just to see if it changes anything.