Just seen this is live! - goto 'Manage Smart Lists' and click SHARE :)

unreal that this isn't a feature!!

Smartlists should definitely be shareable between users. Right now we just spent about 15 min. fleshing out multiple lists within our contacts that we'd like to assign to different users to work through for calls but found that the only way to share this currently is to sit and manually recreate the same filters in each user's account which takes way too long. If it were shareable we could filter and create the lists once and then assign it to the necessary user with just the stroke of a few clicks. Please push this to the top!!