A Heroic Tier Feat gives a character access to one superior implement type - Holy Symbols, Orbs, Rods, Staffs, tomes, Totems, or Wands. The Feat can be taken again for another type. For each type there are four enhancement examples with explanations of all of the keywords included. For example, here's the list for Wands:
Accurate Wand - Accurate
Cinder Wand - Empowered Crit, Energized (Fire)
Dragontooth Wand - Deadly, Unerring
Rowan Wand - Distant, Energized (Lightning)
Accurate is as basic as you would expect, offering a +1 to hit. The Cinder Wand offers an extra 1d10 damage on a crit (scaling upward in Paragon and Epic) along with a +2 damage bonus to fire attacks used with the wand (also scaling upward). A GM could easily build a Glacial Wand or what not by replacing a few simple keywords. Be aware that this system only takes up two pages of the book.
My opinion is that this can be a very powerful option for many builds, but given the specificity of the bonuses a player will absolutely have to be crafting their own implements by now or have a DM that basically seeds what they want for their build.
The cost is almost non-existent, amounting to just a few gold. They can be enchanted just like any other item.
The limit on abilities is whatever is included. Either the implement is Accurate or it has two other abilities, though I suspect a DM could easily take this idea and tweak it to suit.
I think it's balanced vs. superior weapons in that superior weapons are... superior. And so are these! In terms of giving casters a bit of catchup to the options melee and ranged had, yes this does a lot to help.
Deadly - +1 to all damage rolls, scaling to +2 and +3 by tier.
Distant - Range of area and ranged attack powers is increased by 2.
Unerring - +1 attack bonus to attacks against Reflex.