Overall, the new 5.7 drivers will please the majority of ATI users out there, but the performance hit (even if it is small) with the higher memory cards isn't acceptable and might annoy some people. We feel that ATI should have at least given users the option to turn off HyperMemory for the higher memory cards, which should have completely resolved the issue.
Another not-so-great thing about the new drivers is that some of the performance increase claims in the driver release notes are slightly misleading. While we did see a lot of the gains that they mentioned in most of the games, we found many of these increases to be with cards so limited (performance-wise) that they didn't matter. ATI claims in the release notes that the greatest gains in performance will be on cards with 128MB and 64MB of RAM. We found this to be true, but as we saw on the x600 128MB card, almost all of the tests that saw gains still had framerates that were unplayable. Likely, you will see some performance increases on 64MB cards, but you won't be able to run the games at the high settings that ATI claims will produce the highest gains.
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Anandtech