I like them. I enjoy knowing which cards in a pack can represent myself - it deepens my relationship with my cards. Even if a particular spread doesn't call for one, I like to know what mine are. Selecting a significator prior to the actual reading helps me focus on what exactly it is I'm asking about. I pick different significators for different types of issues.
I also don't believe removing a single card from the pack makes that much of a difference in the outcome of the reading. It's like some people are worried that the significator, all of the sudden, over all of the rest of the cards, now holds the key to the secrets of the universe, but you'll never know because the random forces of the Tarot weren't allowed to use it. It doesn't make sense to me, because that single card is the only card now guaranteed to have a spot in the spread, not the other way around. And anyway, the difference between a 1/78 and 1/77 chance of drawing a specific card is negligible in my mind, especially in such an inexact science as divination.
Lots of people are seriously irked by that difference, though.