I think the real issue is that WotC is using this item as a "band-aid" to fix the fact that many builds that suffer from MAD are viewed as underpowered.
Some people may remember the many discussions that took place here in the early days of 3.0 arguing about if the Arcane Trickster is balanced. The basic arguements that the AT is unbalanced are very logical. It gives more power (full caster levels and sneak attack progression, plus more) than another other base class has, there is no rogue/caster build that shouldn't take it, etc, etc. In practice, though, just about everybody has come to terms with the fact that the AT is balanced by its prerequisites (i.e., you must suck to get into the PrC). In many ways, it is indespensible. It is really the only way to make a rogue/caster character viable.
At some point, someone at WotC probably looked at all of the multiclassed characters that are weak because they need to many good ability scores to perform well. To combat this, they made a single item that gave bonuses to all abilities, and lowered the cost significantly below standard pricing to make it more attainable. However, I see two problems with this.
First, unlike the AT, there are no prerequisites. Anybody can use this thing. That means that someone who otherwise would be perfectly happy with three ability boosting items is much more likely pick one of these up to save the extra slots, and piggyback the extra benefits. And I believe getting an extra bump to a couple saves or AC or whatever else is an notable benefit.
Second, I don't think MAD characters are suffering that much. Sure, your Mystic Theurge may need both Wis and Int to cast well, but how is that any worse than your standard Monk or Paladin who needs multiple abilites? The only real classes that can get away with focusing on one or two stats are pure casters and tanks. Add to that the large number of feats and PrCs that have been added in every new splat book to cater to the needs of multiclassed characters (how many Gish PrCs are there in WotC products now?), and I just don't see this item as being necessary.
Just my 2 cents, based soley off the numbers, not actual experience. I don't play with the MHB anyway, so it isn't an issue.