[Epic 4G Q&A, Help & Troubleshooting] mkasick:
I don't know about "one-click", z4root might work, but there's anecdotal reports of it not working on Android 2.2.1. The one-click w/CWM redirector is the easiest way to root and definitely recommended if you want to do anything more advanced (ROMs, etc.). You can always return to stock everything with Odin.

That said, if all you want is root and nothing more, the manual version is relatively simple. It's really just three steps:

Use an exploit (rageagainstthecage-arm5.bin) to get "temporary root" (an ADB root shell).

Install Superuser's su binary to /system/xbin with the appropriate permissions (root.shell 4755).

Sideload Superuser.apk as a regular program, or download it from the market.

In which case "unrooting" is trivial. Just delete /system/xbin/su with root-explorer or something, and after remove Superuser via "Manage applications".

A while back I wrote up semi-detailed directions for doing this. They should work on EB13 with some modification. Here's some notes for EB13:

"rageagainstthecage-arm5.bin", "su", and "Superuser.apk" are all included in the one click package, that's the easiest place to get them.

Actually running "rageagainstthecage-arm5.bin" is the trickest part. There's a few ways to do it, and due to the nature of the exploit, sometimes only one or two of them will work for anyone. You can tell it works if on the next run of "adb shell" you get a "#" prompt instead of "$". Try these three ways in order until one of them works:

adb push rageagainstthecage-arm5.bin /data/local/tmp
adb shell chmod 755 /data/local/tmp/rageagainstthecage-arm5.bin
adb shell /data/local/tmp/rageagainstthecage-arm5.bin

adb push rageagainstthecage-arm5.bin /data/local/tmp
adb shell chmod 755 /data/local/tmp/rageagainstthecage-arm5.bin
adb shell (press return, and type below at the "$" prompt):
/data/local/tmp/rageagainstthecage-arm5.bin

adb push rageagainstthecage-arm5.bin /data/local/tmp
adb push root.sh /data/local/tmp
adb shell chmod 755 /data/local/tmp/rageagainstthecage-arm5.bin
adb shell chmod 755 /data/local/tmp/root.sh
adb shell /data/local/tmp/root.sh

With the last method's root.sh from the one-click package.

Once you have root, and have verified such by getting a "#" prompt with "adb shell", then run:

adb shell rm /data/local/tmp/rageagainstthecage-arm5.bin
adb shell rm /data/local/tmp/root.sh
adb shell mount -wo remount /dev/block/stl9 /system
adb push su /system/xbin
adb shell chmod 4755 /system/xbin/su
adb shell mount -ro remount /dev/block/stl9 /system
adb install Superuser.apk

If you do nothing more, OTA updates should apply just fine. The only caveat is that /system/xbin/su will lose the appropraite permissions, so Superuser will no longer work. To restore it, do the same steps above to regain "temporary root", then run:

adb shell rm /data/local/tmp/rageagainstthecage-arm5.bin
adb shell rm /data/local/tmp/root.sh
adb shell mount -wo remount /dev/block/stl9 /system
adb shell chmod 4755 /system/xbin/su
adb shell mount -ro remount /dev/block/stl9 /system

You shouldn't have to push a new "su" binary since it's already there, and similarly, you don't need to reinstall Superuser.