Just remember that once issued a block altitude all calls to ATC must state the block that you are maintaing, with no reference to your current altitude.
I read recently about the potential of both block altitude and cruise climb availability over the Atlantic. However, given the level of traffic I haven't even dared to ask. Has anyone here done so?
And with regard to cruise climb, I understand that the basic difference between it and a block altitude is that in the former once you climb you can never descend, but are there any other differences?