Hi Tech Legion posted a review on the Sapphire Radeon HD 7770 Flex Edition

AMD doesn't seem to want to change the biggest flaw with Eyefinity, the need for a display port monitor. The only people that I know who own a DP monitor are Apple users. HDMI and DVI are still the most popular interface with all media devices. DP monitors are also more expensive then their mainstream counterparts. Currently, on Newegg.com, the least expensive 1080p DP monitor is $180 while the least expensive DVI is $110 and HDMI is $150. That is at least $30 more that could have been used towards a better GPU or computer component. Luckily, Sapphire has Flex technology that circumvents AMD's reluctance.

The Sapphire Radeon HD 7770 Flex Edition is the latest to contain easy Eyefinity technology. The Sapphire 7770 Flex Edition's architecture doesn't deviate from the stock model. The GPU uses the newest GCN 28nm chip. Core clock is set at 1GHz and memory at 4.5MHz effective. The 7770's GPU contains 640 Stream processors. The Flex edition has 1GB of 128-bit GDDR5 memory. The interface has been reconfigured to accommodate the Flex technology. There is 1 HDMI slot, 1 single-link DVI-D, 1 dual-link DVI-I, and a standard DisplayPort. Out of the box, Eyefinity can be used with 3 DVI monitors. There is also support for 4 monitors using the DisplayPort. The 7770 Flex uses the newest PCI-E 3.0 interface. All of the usual software is supported like DX11, OpenGL 4.2, AMD Stream Technology, AMD Avivo HD, AMD App Acceleration, AMD PowerTune, and AMD PowerPlay.

  Sapphire Radeon HD 7770 Flex Edition Review