Wait for Kepler if I was in your position. I have a feeling they are going to rock this time for mining with the GTX780 having 2304 shaders !
Imagine what the GTX790 will do with 2304 SP * 2 = 4608 shader processors ! I think if their arch did not suck at integer performance then it will surely beat that 7990.
And you are 100% right, AMD drivers always will and always have sucked really hard. I hate AMD with a passion for that fact alone. Nvidia is not that much better and they still have shitty drivers ( but much better than AMD ), pity the GTX580 sucks compared to a 5870 but I think Kepler will change that

Both require end-user expertise to work properly. I'm not sure that qualifies them as "sucking", more like "not user-friendly". Nonetheless, I still miss the days of 3DFX.