I'm still wondering which HA scenarios clusters can't solve, Steve. Please elaborate... Offsite DR doesn't quite fit as a typical HA scenario, but it's still doable with dark fiber and the right SAN gear.

The "best" HA will be a layered approach anyway. Mirroring or clustering for "immediate" HA (such as hardware hiccoughs) combined with log shipping for warm standby at a secondary NOC (to deal with minor disasters, internet service outages, failure to pay the light bill) and offsite backups on removeable SSDs or DVDs in another region or country for recovery from true disasters.