We've used the F4M grade before, can't be sure if this was one of the better grades but some of the Methocell just clumps together and is very lumpy. When I next get to the studio I'll check if the F4M was OK, I'm fairly sure it was.
For those in the UK, I've still got around 120 kg of Methocell in various grades that we are selling off. We had 950g bags on ebay at £16.99 , I can do 1.95kg bags at £29.99 or 5 killo packs at £69.99 plus postage. Weights are just under the kg to save on postage.