When I first started playing magic, the best source of mana acceleration was hands-down Sol Ring.
The world of Magic was moving in a less-powerful direction, although none of us knew that then. The Moxes were far distant machines of myth. And soon Sol Ring would be "restricted" in the various ad-hock playgroups around my high school and a vacuum would be created.
It originally was not uncommon to see Sol Ring tapped to cast…another Sol Ring. That was a part of the game, and we accepted it. But with the restriction of Sol Ring, we looked around for other sources of easy artifact mana.
The best I could find was Fellwar Stone. Not quite as good as a Sol Ring, but still one mana that you could accelerate further into off a tapped Ring already in play. The color of the mana seldom mattered.
What were people accelerating into? Faster Wrath of God, Faster Armageddon, Faster Serra Angel. Or perhaps drawing more cards with Aladdin's Lamp?
Today, we still have Fellwar Stone. My version is from The Dark, which must have cost me an valuable card in trade at one point, because packs of The Dark were then already selling for $8 a pack. Fun fact: the game store up the hill from here (the one that smells like my sweat) just got a box of Worldwake shipped in from locations unknown. How much are they charging per pack? That's right, $8. Overpriced for both!
We come to the modern age, and Fellwar Stone is now available in most of the new Commander Decks. It still has the awesome quote from "Mairsil, called the Pretender." Is there some reason he wasn't made into a card during Time Spiral block?
Evaluated from the perspective of multiplayer commander brings some impressive points.
1) The more players in your game, the greater chance the mana color produced will be relevant to your deck
2) The more colors in your deck, the greater chance the mana color produced will be relevant to your deck
3) Fellwar Stone is one cheaper than Darksteel Ingot, and it will still be one mana cheaper than the new Manalith being printed in M12 Core Edition.
4) If you have a wedge-colored General, Manalith is functionally identical to any of the Shards of Alara Obelisks.
The majority of my decks fall into the 2-color band of commanders, however, and I must unfortunately wonder if this card is still "good enough".
1 mana of acceleration is trivial, isn't it? For a 2 color deck, there is always one of the Ravnica Signets, ex. Rakdos Signet. For more color fixing, 2 colored Allied decks have the Alara Reborn borderposts, ex. Veinfire Borderpost.
What Fellwar Stone ends up being is somewhere in the middle. Slightly faster mana, with a less dependable mana fixing ability.
In more modern magic, the equivalent artifact "mana stone" is Mind Stone. The mana color is completely chucked out the window in favor of a colorless mana combined with possible card draw.
Is the color important? Definitely. So maybe its good enough. And the art is really cool. That's all I can come up with.