installed solaris 10 11/06 with no tricks.

Installation must be done in command-line mode (i.e. exit out of kdmconfig if you're using Solaris Interactive). Installing patch 119376 and the driver for the onboard RAID will prompt for them just prior to completion of disk 1 for Solaris 10 3/05.

We were able to install S10-U1 on a Dell 2850 by disabling the RAID feature on the drives (via the BIOS).

Make sure you turn off RAID mode and use SCSI mode in the BIOS options (Integrated Peripherals or something like that). Performance with a Logical Disk per physical disk is abysmal with the new kernel in OpenSolaris 2009.06 (build 111). (Switching mode will make your boot disk unbootable, so do it prior to installation. ZFS Pools survive the switch, though.)

Just installed Solaris 10 u7 (05/09) on a 2850 as interactive with no issues. X worked fine on the install. (Well, finding a floppy and then an application to write the .img file - hint: try WinImage - took an hour, but other than a bad README file telling me to use dd in DOS to create the floppy for the PERC driver, it was relatively straightforward). Using 4 drives mirrored by the PERC (including boot). NIC's report as e1000g's.

Solaris 10 5/09 installed without issue. Later noted painfully slow network performance with e1000g. Symptom matched http://bugs.opensolaris.org/view_bug.do?bug_id=6781905. Unfortunately, U7 ships with 139556-08, so could not back out. Hacked in driver from 137122-03, and runs like a champ...I suppose until I patch.