Hi,
I use a ppa build of ardour 2.8.4 with ubuntu studio 9.10 karmic. All sound work perfectly and I think ardour is getting to be a serious alternative for home musicians and small studios. The problem is the gui side of things work slow. The lag happens when I scroll down or left-right the screen with either mouse wheel or click-dragging. Gui in other jack apps seems quite fast. My system is as follows:
AMD Athlon 64 X2 5600+
4gb of 800mhz ram
ATI x1950xt with open source radeon driver (2d works quite fast in other apps)
gnome 2.28
gtkmm 2.4-1