Mozilla is slow to load on any system. As for Kit, Gaim is way better, and the new versions of KDE push Kopete instead of Kit anyways, which isn't better than Gaim in my opinion, but anything is better than Kit. KDE is kind of slow though, compared to the likes of Gnome or ones of the *boxes or XFCE4 or what have you, but oh well.

Yes, it does b0rk your MBR. There's no other way to accurately describe it.