SuperHeroHype.com has a great interview with Blade: Trinity director, David Goyer, which includes a little tidbit on working with GDT:
SHH!: Were you at all daunted about taking over from Guillermo del Toro, whose sequel was admired both by horror and comic book fans?
No. Guillermo and Norrington both said that I was ready for this. Guillermo had some doubts when we started Blade II. He was sort of a prot?g? of James Cameron and I remember that he called Cameron when we were embarking upon his first action set piece, so I also placed a call to Guillermo when we started our first action shot. Maybe it’s hubris, but if I’m too plagued with doubt than I shouldn’t be directing.