[Transformer TF300T General] abczhou:
Finally i think i succeed. for people like me who have broke root in TF300T, please follow the procedure with http://matthill.eu/mobile/root-transformer-prime-jellybean-update/ , but important thing is, DON'T use the sufile.zip provided there. (su file size is different with OP's) I succeeded with the "su/busybox/Superuser.apk" combination which provided by OP in his first post of this thread.

Also attach my operation log, wish it is helpful.

Directory of C:\motochopper

04/12/2013 10:42 PM <DIR> .
04/12/2013 10:42 PM <DIR> ..
04/09/2013 08:23 AM 162,816 adb.exe
04/09/2013 08:23 AM 1,226,659 adb.linux
04/09/2013 08:23 AM 208,192 adb.osx
04/09/2013 08:58 AM 96,256 AdbWinApi.dll
04/09/2013 08:58 AM 60,928 AdbWinUsbApi.dll
04/09/2013 08:46 AM 1,867,568 busybox
04/09/2013 12:27 PM 1,283,460 pwn
04/09/2013 09:24 AM 1,933 run.bat
04/09/2013 08:51 AM 2,103 run.sh
04/09/2013 08:42 AM 91,980 su
04/09/2013 08:42 AM 969,701 Superuser.apk
11 File(s) 5,971,596 bytes
2 Dir(s) 20,423,307,264 bytes free

C:\motochopper>adb shell
shell@android:/ $ exit
exit

C:\motochopper>adb push C:\motochopper\su /data/local/tmp/
696 KB/s (91980 bytes in 0.129s)

C:\motochopper>adb push C:\motochopper\Superuser.apk /data/loca
1163 KB/s (969701 bytes in 0.814s)

C:\motochopper>adb push C:\motochopper\busybox /data/local/tmp/
1180 KB/s (1867568 bytes in 1.545s)

C:\motochopper>adb shell
shell@android:/ $ /system/usr/we-need-root/su-backup
/system/usr/we-need-root/su-backup
shell@android:/ # mount -o rw,remount /system
mount -o rw,remount /system
shell@android:/ # chmod 6755 /data/local/tmp/su
chmod 6755 /data/local/tmp/su
shell@android:/ # chmod 755 /data/local/tmp/busybox
chmod 755 /data/local/tmp/busybox
shell@android:/ # chmod 644 /data/local/tmp/Superuser.apk
chmod 644 /data/local/tmp/Superuser.apk
shell@android:/ # ll /data/local/tmp/*
ll /data/local/tmp/*
-rw-r--r-- shell shell 969701 2013-04-09 08:42 Superuse
-rwxr-xr-x shell shell 1867568 2013-04-09 08:46 busybox
-rwxrwxrwx root u0_a88 17371 2012-07-01 16:54 init.rc
-rwsr-sr-x shell shell 91980 2013-04-09 08:42 su
shell@android:/ # cp /data/local/tmp/su /system/bin/
cp /data/local/tmp/su /system/bin/
shell@android:/ # ll /system/bin/su
ll /system/bin/su
-rwsr-sr-x root shell 91980 2013-04-15 23:49 su
shell@android:/ # cp /data/local/tmp/busybox /system/bin/
cp /data/local/tmp/busybox /system/bin/
shell@android:/ # ll /system/bin/busybin
ll /system/bin/busybin
/system/bin/busybin: No such file or directory
1|shell@android:/ # ll /system/bin/busybox
ll /system/bin/busybox
-rwxr-xr-x root shell 1867568 2013-04-15 23:49 busybox
shell@android:/ # cp /data/local/tmp/su /system/xbin/
cp /data/local/tmp/su /system/xbin/
shell@android:/ # ll /system/xbin/su
ll /system/xbin/su
-rwsr-sr-x root root 91980 2013-04-15 23:50 su
shell@android:/ # cp /data/local/tmp/busybox /system/xbin/
cp /data/local/tmp/busybox /system/xbin/
shell@android:/ # cp /data/local/tmp/Superuser.apk /system/app/
cp /data/local/tmp/Superuser.apk /system/app/
shell@android:/ # ll /system/app/Superuser.apk
ll /system/app/Superuser.apk
-rw-r--r-- root root 969701 2013-04-15 23:51 Superuser.apk
shell@android:/ # reboot
reboot