
On my fourth one of the evening and it's not so noticeable now, probably more down to me than the beer though! SWMBO says she can't taste it but there's no doubt about it for me, there was a real banana element. I've got another can of Coopers stout in the brewing cupboard I was saving for an Imperial experiment but I might try doing the cool ferment again to see if I can reproduce the taste/smell I got this time.
I recall earlier in this thread some discussion of the banana thing but couldn't find it again when I had a quick look through. It definitely wasn't there the first time I brewed it (in September, I think) when the temperature was higher. I've just had a look in to it and apparently the smell of bananas is down to an ester called isoamyl acetate, try Googling it with yeast or brewing in the search if you want - the articles I've found are a bit heavy after a few beers but worth a look if you've got some time.