Here is what I believe is a better way to root the Acer Iconia Smart  
(Acer_S300_1.000.24_AAP_GEN2   firmware).  
 
There is a thread about Rooting the Acer Iconia Smart here:
 
http://forum.xda-developers.com/showthread.php?t=1263244
 
But what if you just want to root, and you do not want to loose the factory recovery?  Flashing a 3rd party recovery is always more risky.
 
I tried installing the referenced su-2.3.6.3-efgh-signed.zip from the factory recovery, but it failed with an invalid signature.
 
So here's what I did:
 
Download zergRush from this link:
http://forum.xda-developers.com/attachment.php?attachmentid=841876&d=1325678 726
(xda-developers registration required.  Other links do no seem to work anymore. You must have version 4 of zergRush)
Parent Article:
http://forum.xda-developers.com/showthread.php?t=1321582
 
You also need ADB, and Windows users may need USB drivers.
 
If the other links die, the C source code for zergRush is here:
https://github.com/revolutionary/zergRush
Build it with:   agcc zergRush.c -o zergRush -ldiskconfig -lcutils
 
Unzip DooMLoRD_v4_ROOT-zergRush-busybox-su.zip
 
On Windows, you may be able to use the included runme.bat, but I just opened the .bat, and did the same steps manually -- Hint to make it faster:  Open two terminals and do  ./adb shell in one, and do the ./adb push steps from the other.
 
zergRush should succeed.  At this point you have a temporary root.  If you only need a one-time root, stop once you have ADB running as root.  Do what you need to do, an remove zergRush. When you reboot, your phone will be unchanged (except, of course, whatever you needed to do as root).  This makes your phone safer from both intentional and accidental changes than a permanent root.
 
If you want permanent root, you can then install su, busybox and Superuser.apk.  Move the files into the proper places, and change permissions exactly as shown in the DOS .bat file.
 
When you reboot, Google Play will show an update for Superuser.apk.
 
DISCLAIMER:  I am not telling you to root your phone.  That decision is yours.  I believe that what is described above is safer than installing 3rd party recoveries, but Warnings about permanently damaging your phone apply.  When you are root, you are responsible.