As SMEserver 6.0 is no longer supported I've been migrating sites to 7.1, including those already on 7.0 (this can be done by a yum update).
I had a really good experience with a new Dell server - no problems, built the mirror fine, and even recognised the UPS connected by USB once I had enabled nut in the configuration.
I've also had some hiccups....
One machine has lost its access to an IDE tape drive. Haven't really worked that one yet. We had the same problem moving from 6.0 to 7.0, but I'm not sure what is going on now.
Another older HP server caused other problems. The new kernel has include I2O which is a direct wa of working with the Adaptec disk arrays. This meant that disk devices changed from /dev/sd[ab] to /dev/i2o/hd[ab]. It handled the root and boot devices fine (probably because they were identified by labels), but the install didn't like by second array which was mounted - I had to get in and edit /etc/fstab and reboot.
Unfortunately there was yet another problem (which is definately a bug) in that GRUB wasn't installed on the the boot MBR. A bit more messing around and that was fixed.
And finally, there is an Initio Corporation INI-A100U2W SCSI card with tape drive installed which isn't recognised. I'm still working out how to get a kernel module installed for that.
.. That wasn't too hard. Install CentOS4.4 server on a machine, get the kernel source SRPM, as per release notes and update the config to create a module for a10u2w in kernel/drivers/scsi and then copy the .ko file into the /lib/modules directory for the kernel and run depmod -a then modprobe the module.