Is this land at an acceptable power level?

Certainly doesn't seem overly strong. I think it might be underpowered.

I think it'd probably be fine to replace the second ability with ": Add one mana of any colour to your mana pool. Spend this mana only to cast an artifact spell." (No need to exclude Sunburst artifacts either.) It's no Ancient Ziggurat.

Of note: if you replace the last line with Alex's suggestion, you might as well remove the first line, too. Unless you believe there is value to specifically adding ...

Er? Noo, the first line is quite important - it allows this to be used to cast creatures, and sorceries, and so on.

Oh whoops. Too true.