I think there are different reasons for needing task killing/managing apps than just "how many can my phone handle at a time". Each one is based on how and where you use your phone.
I am actually running a different task program called Advanced Task Manager. I also run this in conjuntion with 2 other apps called Locale and Power Manager.
For me these are all essential. None seem to have any effect on the speed of my Driod phone but all 3 are key in keeping it running smoothly and keeping my battery from prematurely discharging.
I assure you this is true but not for the reasons everyone will assume. The tasks weren't klling my my battery. My office was. My office is almost 20 feet underground. I can barely get any cell signal at all and I do not have a wireless access point nearby.
If my WiFi is turned on it will kill my battery quick while looking for networks to sync with. My phone reception is good enough that I eventually get my e-mails and get some part of my phone calls and can make it through the day on a single charge as long as I don't have the GPS or WiFi enabled.
My Advanced Task Manager program has an auto-kill adjustible timer and the option to create exceptions. This way every 30 minutes ATM kills any app that is not in the exception list. This ensures that I still get my e-mails, phone calls, calendar updates, etc. but turns off everything else. This ensures there are no apps running that might turn on my GPS or WiFi or Bluetooth.
Locale automatically turns on/off apps based on battery status, calendar date, contact, location and time. I use this to automatically turn on my Wifi, Bluetooth and GPS during the hours that I am out of my office. This way the only time these are running they actually have something to connect to and aren't just killing the battery.
Lastly, I run Power Manager (free) to have a widget that I can toggle Wifi, Bluetooth, GPS, Sync, and Brightness from one of my hompages in case I need these during the normal "off" hours.
The main reason I chose these 3 specifically was not because apps were killing my battery or making things run slow, but apps were actually killing apps. There are just as many good apps out there as bad apps. I do not intend to run every single one I want to try through the ringer. I had problems with multiple apps trying to use the GPS and my navigator wouldn't connect. If I kill all of the other GPS apps or power cycle the phone it works fine. (Or if they were never running in the first place then I wouldn't have this problem.) So by shutting down apps I am not using every 30 minutes I avoid a lot of program conflicts. This also makes less than perfect apps work just fine for the few minutes I need them. And in the meantime the apps I need to have running at all times keep going strong.
Before I got this balanced my battery life was terrible and the first week I had my phone I had to pull the battery out once and power cycle it at least 7 or 8 times. Since I have gotten this set-up I haven't had to do either and my battery is typically at 50-75% by the time I get home late at night. (Even though it was syncing all day while 20 feet underground.)
Hope this is helpful to someone. Just wanted to put my own spin on uses for task killers and power management.
Nice forum you guys have here.