For a counterpoint, I've now migrated 3 customers to DP8, not counting my crash'n'burn environments.
The only problem we've encountered has been the IDB not backing up correctly after the upgrade. (Which I've now resolved, I think.) I think there is a bug in the migration process. Things to be aware of:
Run omnimigrate.pl -start_catalog_migration when you have a lot of time to spare, and I think do it when you aren't running any backups.
If the database consistency check fails, try:
omnidbutil -remap_dcdir ;
omnidbutil -fixmpos ;
omnidbutil -remap_dcdir
And if the internal database backup fails with an error 1314, remove the "OWNER" line from the barlist file.
The performance of the new database is outstanding; where before there would always be a single CPU running at 100% utilisation (and all other CPUs idle) during intensive client backups, now the load is a tiny fraction and it is spread across 8 processes.
But other than the database upgrade, no, I don't see anything special in DP8 that's not there in DP7 + patches.