I don't know about anyone else, but I have been plagued with huge numbers of crawl errors in my Webmaster Tools page. These are usually 404 errors which were fixed months (and sometimes even years) ago. The errors would usually remain persistant and never dissapear, even though they were supposed to upon re-crawling. Now, Google has updated their Webmaster Tools interface so that you can mark errors as "Fixed". In doing so, the error is removed from the crawl errors page. This probably also marks them for re-crawling so that Google can verify the error was fixed. No more fucking annoying crawl errors in your face when you visit Webmaster Tools!!