Verizon employees have been instructed by their technical support teams to install ATK. I don't know whether this is oficial VZW policy, or more word-of-mouth, but I have heard this from enough sources that I believe it is true. While they shouldn't be installing anything on your phone without asking you first, they are doing it in the spirit of service, based on what they believe to be good information.
It's no worse than the other bloatware that comes preinstalled on the phone. In fact, it's better because you can uninstall it.
As to whether you need a task killer... You don't. Android is not Windows. Programs not in use will remain resident in memory and will appear to be starving your phone for resources. They aren't. Android will manage tasks for you, and do a better job of it than you can do on your own.
Once in a great while, you may find that a program gets stuck and needs to be killed (e.g. Cardio Trainer got stuck on my phone yesterday. I noticed it was active and my battery meter showed it was consuming a disproprtionate amount of power). In this rare case, the built-in task manager usually works fine. As an alternative, you might consider something like SystemPanel, which allows tasks to be killed, but serves other purposes as well and doesn't normally remain running when not in use.
By the way, I used to use a task killer all the time. I argued that they were necessary. I was wrong.
