Gonna try pureeing frozen bananas tonight.
I freeze bananas unpeeled then nuke them if i want them defrosted right away; they become this very concentrated puree.
I freeze with the skin on because I'm planning to make banana bread, for example. But if you're going to puree them frozen, I'm wondering if you might have trouble peeling them. Seriously, it's bananas, let's not overthink this. I vote for unpeeled.
I used to freeze with peel but had trouble peeling so started freezing unpeeled and as Jenny said nuking them,
I've never heard of/tried the microwave trick. It sounds great if you have a microwave. I have found it difficult to remove peel after freezing, so I take the skin off and pop in a baggie before stashing in fridge.
If you're going to freeze them for a puree to eat like a sort-of sorbet, then I'd peel them before freezing.
If you're going to freeze them for a puree to use for banana bread, then do what Jestei does. or you can just leave them on the counter for a while to defrost.
I freeze them with the peel on for smoothies and just cut them in half and peel this way while they're frozen when I'm ready to use. If you have difficulty, you can always just use the knife to help you peel of the skin!