Due to several Problems during installation on a box, I installed RH6.1 four times ;-(. The installation of about 730MB took 12 Minutes in text-mode. In graphical mode this abou 40 minutes. I did a quarter-hour installation in textmode via NFS on another box some days ago and from CD on a Siemens Scenic Mobile 360.
We are making efforts to speed up the next graphical installer.