IMO aMSN is pretty much the desktop experience on MSN but very slow to launch, works ok once is up and running. If you plan to have it open all the time is not bad.
Pidgin is lighter, faster and still has a lot of settings, but less than aMSN. I use Pidgin a lot and think is a very good app.
Haze and Butterfly are buggy at least to my experience. They connect right away on WiFi but once I leave my office and go on EDGE both of the will disconnect and will never connect again unless I reboot the phone. For me these plug ins have not been reliable at all but is just my experience, maybe is human error.
Hope it helps..
