I'm seeing a problem with poor performance on SCSI drives. IDE drives take about 15 minutes to do an "everything" install from HDD. The same install on the same computer except using a SCSI HDD takes about 40 minutes. When I try hdparm -t /dev/hda I get between 16 MB/sec for laptop drives to 25 MB/sec for EIDE 100 drives. The same test on /dev/sda with 15K rpm SCSI 3 Seagate Cheetah drives produces 5 MB/sec.
The qa0314 and later trees are known to have this issue solved (the default queue depth in the RC2 release was 1 and that severly limited performance, upping the queue depth to 32 has helped tremendously).