I'd say it depends too. The situation described, definitely sounds like the best thing to do is to take your place in traffic and wait. Filtering between lanes is dangerous...

Now then, if traffic is a huge snarly mess and cars aren't going much of anywhere I do feel that if there is space, one of the advantages of being on a bike is that I don't have to sit in it...... I wouldn't filter up between two lanes in this case, but I'd feel free to use the shoulder