Just chiming in to say that the UAFX amp sim pedals are all stereo and the four I have work great in the stereo insert. The Poly Ample, Walrus Mako, and Strymon Iridium are (or can be) stereo so I imagine they are fine in the stereo insert too.
But, besides the effect units discussed here so far, there also seem to be more and more amp sim pedals that are mono in and stereo out. Examples: Tonex, Tonex One, the three Friedman pedals, Tone King Imperial, Kemper Player, Nano Cortex, Boss IR-2 and Boss IR-200.
