In the case of removing a judgment where multiple derogs exist, a lot depends on the spread between the individual entries. In any event, you have to nail the most recent entry for it to have any significant effect.
Let's say you have three judgments, from 11/07, 08/07 and 12/06. You get the one from November of last year removed. You probably won't see too much of a gain, because there's still a judgement from just a few months ago left.
If OTOH, the three are 11/07, 02/06, and 11/04, you would likely see more of an increase, because you've gone from seven months since the last major derog to 2.5 years.