I Wouldn't trust the
Spirit Shaman Handbook, It downplays the significance of Wisdom in favor of Charisma, even the your access to spell levels is based off Wisdom while only the DC is based off Charisma.
Excellent caster class. Cast like a Bard/Sorcerer, progress in spell levels as good as Cleric, Swap spells known each day. Awesome.
Class features are so specific, however. I never personally liked the flavor. Except Blessings of the Spirits, that's good stuff. Recall Spirit is nice too, but so timing specific.
If the Sapphire Hierarch didn't have the Law domain as a prereq, I think it would make a cool Spirit Shaman/Totemist build. Perhaps handwave that away or take a single level dip into the Contemplative PrC.
Since the class abilities (In my opinion) aren't that impressive, I'd even recomment Mystic Thurge as a Spirit Shaman/(Something Arcane) build.
Geomancer would be another flavorful build of Spirit Shaman/(Something Arcane), more for the class abilities than the casting.
...Yeah, the only things I can think of PrCing the Spirit Shaman into would be duel caster builds. And in that case, Spirit Shaman would be a much better option than Cleric or Druid, IMHO.
How about looking into DMG II's Companion Spirits concept? Could be a good synergy with the Spirit Shaman and benefit everybody.