I've been using BioPellets for a month now and had to supplement GFO. I think it works but not as well as claimed. The store that sold me the BioPellets was even claiming that in 6 months GFO will no longer be around due to the popularity of BioPellets. What a crock!
GFO is still King in my book for removing phosphates. Once every 3-4 months to change GFO is not a heavy task, so I don't know why anyone would complain about that since it'll keep your tank in check.