I have AmiKit installed, and found it very slow, so I switched Dopus off, as well as loads of other stuff that I don't use, so I now just have a nice looking workbench, and whilst it is still slow, it is a little faster than my A1200 so I can use it if I needed to, but I don't use it as I don't really have anything to use it for.
I certainly wouldn't get rid of the Amiga. I don't see why I would want Windows running in the background of my Amiga, so AmiKit/Amiga Forever/UAE is not a replacement for the Amiga, just an extra thing that comes in handy sometimes.