Well, everyone's different aren't they and, given that, it's probably better that men don't assume that their shouts and wolf whistles are universally welcomed.
Personally, when I was younger I found it embarrassing and intimidating to be shouted and whistled at by a group of leering men.
If a man stood in front of me and didn't let me pass, I would find it intimidating and possibly threatening. I don't think a wolf whistle should be treated as sexual harrassment in normal circumstances but if it is accompanied by lewd comments and invasion of personal space, it is, in my opinion, unacceptable.
I think it's rather sad that women feel the need for their attractiveness to be validated in this way - particularly as I feel this sort of male behaviour is not really meant to be complimentary.