I have never seen much of a positive result when working with third-party app killers. With this task manager being native to the phone, users can access the clear and simple layout to see at a glance what's running and can be closed with no ill effects (Notification screen > Quick Settings > Total Memory). Once in the app, users can stop specific applications or choose to kill them all at once.
A subtle touch that lets you further customize your EVO experience is being able to customize when to have the phone notify you of memory issues (Notification screen > Quick Settings > Total Memory > Menu button > Advanced > Notifications). Once here, you can also see the additional options available to you.
So far the only tweak I would like to see pushed out is the ability to "protect" certain running apps that have your permission to do so. Examples would be those of us running Juice Defender or a homescreen replacement like LauncherPro or ADW. Other than that, this is an excellent memory (and sanity) saving approach to managing the EVO 3D's on board storage.