By definition they stall the Senate, that's what they're supposed to do and the reason they're utilized. In theory they can be used for the opposing sides to have extra time to talk things out and come closer on an issue, but in practice that usually isn't how it works. They're typically just used to prevent the other party from getting anything done.
The entire reason for the filibuster is to delay and stall the Senate. It is nothing more than a delaying tactic employed by the losing side to dig in their heels and thumb their noses at those who would win. It can paralyze Congress to the point of a stand-still, and in my opinion is bad for our country as it prevents forward momentum.
In the good old days it used to be fun to watch a filibuster because anyone objecting to a bill had to actually stand up and occupy the floor and talk for hours. That requirement has been done away with, and now it is far easier to have a filibuster because it just gets recognized. I don't know the current mechanics of it, but it requires only a higher vote to overcome the filibuster. So in the recent past the filibuster has been vastly overused as a stalling device and has enabled the GOP to block almost all legislation from moving through Congress. They succeeded in getting virtually nothing done.
They stall important business and keep it from getting a true vote. There is no reason that something that only needs to pass by a majority should be prevented from a vote because of a procedural hurdle that both sides exploit for political gain (depending on which side is in the minority).