Hi Sits,
I can confirm that this machine (single processor configuration at least) runs SME7.0RC1 VERY well, with both cores of the Xeon recognised, and an SMP kernel running. The older SME6.x won't install because the hardware is too new to be recognised.
The only problem I have found so far is that (like SME6.x and apparently because of a Samba bug) ibay shares accessed via Samba shares can only receive files up to 2Gb in size. Over this limit a write error occurs. I know that scp works OK for larger files, and rsync worked on large files under SME6 so it should be OK here too I expect.
Dell supports and supplies RHEL4, so if you order the linux configuration at order time (without ordering RHEL itself), you still get some configuration tools and extra configuration documentation for RHEL4.
I hope this helps.