How well will the AMD Radeon HD 7950 gpu perform on Linux?

The time has come for me to upgrade my aging gpu (9800 gt). The AMD 7950 has caught my attention because of the attractive price with pleasing benchmarks. But it is common knowledge that AMD GPUs have poor support on Linux. What sort of performance can I expect, with say, the latest version of Ubuntu? Will I have issues starting X. Will I have issues with a dual monitor setup? Will basic games such as minecraft or neverball play as expected without problems? Will there be any issues with video playback or flash? I tried doing some research with how this card performs on Linux, but google lacks any usable resources. If the 7950 is completely useless when paired with a Linux system, can someone suggest a comparable nvidia gpu for the same price range with similar performance?