With the newly released Bluefruit EZ-link board and shield, you can download your programs without the cable (freeing the tablet for charging).
For the Bluefruit EZ-link board (above), wire to Uno per the tutorial here.The shield (below) is a little easier to use since it just plugs on top, but I had a breakout handy and it only takes a few wires to connect it
The benefits of using Bluetooth is that there's no wonky driver nonsense. Bluetooth is built into every single tablet and replaces the "FTDI" or "Uno" driver requirements!
If you go to the Windows 8 desktop, the Bluetooth icon is in the notification area, lower right (you might have to tap the little up arrow to see all the icons, the Bluetooth icon is a blue oval with a B on it). Select Add a Bluetooth Device from the menu. You may need to press the Bluefruit "Pair" button on the circuit board. Your tablet should detect something is pairing and load the driver for you (warning - this can take a minute). If your Bluefruit is listed but will not connect, delete the current entry, press the pair button, and it should rediscover the device and allow pairing.
To make sure you have the right COM port, right-click (or press and hold with touch) the Windows icon in Windows 8.1 lower left corner of the screen. Select Control Panel. In Control Panel select Devices and Printers. You should see an Adafruit Bluefruit icon near the bottom of the icon list per the Bluefruit tutorial. Double click the Adafruit EZ-Link icon then click the Hardware tab. It should say: Standard Serial over Bluetooth link (COM3) - it might have a different COM number, no problem, just note it.
In the Arduino IDE, go to the Tools Menu, then Serial Port, then select the COM port you just discovered which belongs to Bluefruit.
If your circuit is built correctly, you can now remotely send a program over Bluetooth to your Uno. The capacitor from Bluefruit DTR pin to the Uno Reset pin is required to have the sketch auto-reboot when loaded. If you do not have one, just push the Uno RESET button after the sketch loads.
Note the load process takes longer wirelessly than with USB. It will work, it just takes 60-90 seconds.