It's a long-term turtle build. It shines best at ECL 11-12, where the ghost's Malevolence and Telekenisis are at par with a straight Sorceror/Wizard casting Magic Jar and Telekenisis, or at high epic levels, where 5 class levels don't matter too much. Below that, and the Ghost has a 50% or less chance of self-ressurecting (taking 10 fails at CL 5 (DC 16; rolls 1d20 + Ghost's HD)). Above that, a Sor/Wiz can duplicate most/all of the Ghost's abilities (depending on selection of Ghostly abilities and the Sor/Wiz spell list) while the Ghost will be stuck 2-3 levels of spells behind (and 5 caster levels - that 11th level Wiz casting Fireball does 10d6 damage for one of his middle slots, while the ECL 11 ghost is only doing 6d6 for one of his highest slots). Moreover, the Ghost can't use any touch spells (well, at least not without Spectral Hand, Arcane Reach or some other way to avoid the "relying on touch" aspect of touch spells), so isn't nearly so good with party buffs. Even further, it's almost impossible to re-equip the ghost after character creation (Must hire Plane Shift or something) which pretty much rules out anything with costly material components (hence VoP being a good choice).
It's a costly way to go about gaining immortality. Makes for a great scout (go etherial for a standard action .... or rather, go non-etherial for a standard action), and a good recovery expert (always recovers personally, so can regroup and ressurect the others), but makes a poor addition to the combat team; can only self-heal (by using Neutral Cleric levels, rather than Sorceror levels) using a Harm/Inflict spell that won't help the rest of the party one iota.