For about $240, you get a better card than the more familiar Radeon HD 7870, based on AMD's Pitcairn GPU. The HD7870 PCS+ Myst Edition manages to almost catch up to the first-gen Radeon HD 7950 (without Boost functionality), which is more expensive.
Overclocking, even without a GPU voltage increase, makes this Tahiti LE-based board as fast as a Radeon HD 7950 with Boost. Although you could always overclock the pricier Radeon HD 7950 as well, the Myst Edition certainly offers better bang for your buck, particularly if you're on a strict budget. At the end of the day, you get a great deal on a card that’s more Radeon HD 7950 than 7870.