Tungsten putty is very good stuff for applications where you have a precise need for a certain amount of weight and where the amount of weight you need varies significantly from pool to pool. That is to say, it is easy to add or subtract the amount of putty used to meet conditions . These are the plusses.
On the negative side, it seldom stays affixed to your leader as well as properly crimped shot, regardless of the type of shot. It will sometime slide down the leader or simply disappear altogether. This is especially true in situations where conditions require a more forceful casting stroke, like on smaller streams with fairly tight canopies.
I think the perfect use of the putty is to place it above a single small shot on the leader. This does away with the sliding issue and allows you to do the add and subtract thing, which can be very useful.
I came to really like the putty once I figured out the best ways (for me, anyway..) to make use of it.