I just wondered if anyone had any time scales on the length of time that it takes Google to process a disavow links report and for you to see the difference in your rankings both positive and negative?
They have to get the list, spider the pages the links are on, then run Penguin again ... It's not anything like an 'overnight' fix.
There's a thread with a longer more detailed quote containing the info from John Mu here somewhere, but I'm not sure where off the top of my head ... The above is 'the short version' of what I remember being quoted from him by someone here.
To paraphrase what he says... using the disavow tool adds something similar to nofollow to the links you've disavowed, so if you chose applicable links, disavowal will be effective. He adds, though, that "you should... keep in mind that it takes quite a bit of time for this to update". Google needs to recrawl those links and also to "update the Penguin algorithm data".
As TMS suggests, this combination of recrawling the pages and updating the data indicates that we'll see abrupt changes, widely spaced in time.