Agreed. I always assumed the the end-user terrible GUI itself is for real developed by some other team that that developing the core application. It really looks like the GUI adds up all the slowness of McAfee. Things may have changed in the mean time and I don't want to sound extreme, but I tried it two years ago and I honestly found it unusable, literally.

My experience is that when idle, cpu usage between a machine with corp McAfee and without ir is quite identical. If you desable the on-access scan, also normal operations are just as fast in both machines. If, instead, you enable on-access scan, then you experience some general minor responsiveness, but such difference is less and less perceivable as you move to faster processors. It also seems to me, but I have not tested it extensively, that multi-core processors make the difference unperceivable most times.

Provided it does not decide no service is allowed to run because they are viruses, of course. In that case, pretty much everything, from loggin on to copying files to/from a usb key, takes such a long time. An infinitely long time: you just can't do those things .
Guys, what a nightmare.