In the past two weeks I've made two mosaics with ACP, and they came out very well. I've never done a four-panel mosaic before, so this one of the Heart Nebula is my first: http://astronomy.mdodd.com/nebulae-26.html While I was in the celestial neighborhood, I did a two-panel Soul Nebula: http://astronomy.mdodd.com/nebulae-27.html
I appreciate very much that ACP adds the target coordinates to the FITS header. One of the steps to build a mosaic in PixInsight is to solve each integrated panel. PixInsight's ImageSolver script retrieves those coordinates from the image -- they are still there even after sub calibration, star-alignment, and integration. This is a huge convenience, saving me the extra work of opening the ACP plan in an editor to get them.
Also, ACP's pointing model and "every image centered" feature is great for mosaics. I have my max pointing error set to 1 arcmin, and the resulting panel subs are framed really well -- so well that I've set the panel overlap in SkyX to only 10%.
Finally, I like ACP Planner's ability to import SkyX mosaic data. It's great to be to plan a mosaic in SkyX, then import it into Planner (and remember to set the camera PA and change the target name from "mosaic"), then save the plan to a .txt file. Piece o' cake!
I'm still using ACP's old-school console interface, which works just fine for my needs. Thanks Bob!
--- Mike