I've installed the latest Firefox and Chrome on my Windows 7 64 PC (using a wifi connection to my ADSL2+ router) recently.
In both cases loading various commonly visited sites such as wikipedia, youtube, superuser etc regularly timed out with a "server unavailable" error, requiring 2 or three retries before eventually loading the page. This made using these browsers a nightmare and sent me straight back to Opera (reluctantly).
The same sites in Opera load without error in at most 4-5 seconds.
After some research I eventually found that these browsers both offer a prediction/prefetch "feature" that purports to speed up the loading of web pages.
As soon as I disabled prefetching/prediction, magically, all pages now load without error and in at most 4-5 seconds in both browsers.
In my experience this is a huge negative for a user moving to a new browser, only to find pages now load much more slowly and often not at all.
