I have an ASI120MM-S, and it worked perfectly out of the box in PHD, PHD2 and Metaguide (then I installed an older ZWO driver for it and lost connectivity, but that is an entirely different thread I started - with a happy ending thankfully!

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I find that PHD2 runs the ASI equally as well as Metaguide, in either native or WDM mode, though I find the PHD2 interface much simpler and intuitive than Metaguides clutter. Metaguide offers a little more "fiddle" control, but not sure where I need it yet as everything just works as it is supposed to. PHD2 seems also easier to set the camera settings (gain etc).
Both work, I just must be one of the PHD2 disciples (when not using MaxIM DL guiding, which is better than both!)