I've seen lots of spreads that use significators. And I usually like those spreads.
I also see a lot of people saying they don't like using them because it takes a potential card away that might otherwise show up with an important message in the spread. I suppose I understand this line of thought, but there are 77 other cards to choose from. The likelihood that taking one out will really mess up the result isn't very high, in my opinion. I mean, the Tarot, to me, is a very fluid system, and I think if a message absolutely had to be delivered in a spread, it'll still come across with or without a significator having been removed.
However, there is a solution to this dilemma, and that is to have the querent select a significator ahead of time, and then have them shuffle it back into the deck. This way it can still show up in the reading, and if it does, it will draw special attention to that spot.
Or, if you don't like significators, but wish to use a spread that requires one, just draw a random card for that spot, and whichever card comes up can maybe tell you about the state of mind of the querent.
One interesting method of divination that uses significators is that described by Crowley in his Book of Thoth. In that method, the significator is selected, shuffled back into the deck, the deck is cut into several piles, and then the reader must divine the location of the significator based on the querent's question and the predetermined nature of each pile, and using the remaining cards in the pile that it's found to formulate a conclusion. These and similar steps are repeated several times. (I've simplified this a great deal, but I think you all get the general point, that there are creative ways to use significators for Tarot readings).
I've probably repeated somethings that have already been touched on; hopefully I'm not being too redundant.
I suppose it boils down to personal preference, but I do believe that significators can be very useful, if for no other reason, than for gaining a deeper understanding of your personal relationship with your deck. As I've said before, I'm always aware of what my significators are, regardless of whether or not I'm using a spread that requires me to set one aside.