The thread's not dead! Unlike these guys.
Vampire spawn are basically weak vampires, which shouldn't be surprising. They are available slightly earlier (4 RHD), but lack some of a vampire's abilities. Amongst other things, that means no spawn-creation.
It does, however, still result in a low- to mid-level character with at-will Dominate Person, fast healing, DR, energy drain, good ability scores, and the valuable undead type. The bad RHD compensate for this, so in the end I feel like +0 LA is appropriate.