Divers-
There are some defininate (sp?....Im too lazy to pull up dictionary.com) pros and cons to sinking leaders.

I fish them alot in the summer time. I feel that they give me an edge on summer fish when they aren't totally focused on a straight dry line presentation or when I am fishing over heavily pressured fish.

Sinking leaders do a great job of bring the fly down to the fishie's zone but because they lack the mass to hold the fly down on the swing, the fly tends to ride up much quicker then it would when fished with a standard sink-tip.

I have found this presentation to be very effective in the summer-time.

However, I have yet to give them a go in the winter because I've never found winter fish to be overly receptive to fly lifting to the surface so I feel they provide you with a severe disadvantage under your typical winter conditions.