I'll let you know in a few weeks, after my players encounter one.
I think it's definitely on the edge. The NPC I converted to the class wasn't too bad because he wasn't made to maximize its potential (and he was an elf, making the Con problem a little less thorny)
On the other hand, the hit on saving throws makes them especially vulnerable to all manner of things. I predict that most characters with this class will be the proverbial eggshells armed with hammers - they will hit hard and go down easy.
Consider a Wiz5/SA5. He can cast 7th-level spells, sure, but he can have a max of 13 ranks in concentration, and say +4 from Con due to good stats and/or an amulet or something. His Concentration DC for casting that spell is a 26, meaning he needs to roll a 9 or better to cast it.
Think about that. When he uses a 7th level spell, it's almost like every target has SR 22. He's going to lose almost half of his 7th level spells. Or he can take 7 points of damage - but on average he's only got 60 hp, so he can't afford to keep that up for long. His Reflex save is a miserable +2, his Fort save is not much better, and he's even going to have trouble resisting enchantments and other Will-based effects.
I wouldn't worry about items. The earliest you can get into the class is 5th level, by which time most of the item feats are available to you already. You'll be able to get Craft Ring a whopping 2 levels early, it's true, but I don't think that will kill anything.
J