We have tested the Alfa AWUS036H 1000mW long range WiFi USB adapter on Windows 8. There is also a range comparison to the on-board WiFi card at the end.
On our Toshiba notebook, it was plug and play, no driver needed. In this video we also show how to install the driver manually in case it is not plug and play for you (for this part, expand the video window or put in full screen mode to see on-screen text clearly). There is no official Windows 8 driver for this product yet, so this video details how to install using the Windows 7 driver. The Alfa Client Utility program is not currently compatible, but you can use the Windows 8 Connection Manager to scan for and connect to networks. Let us know in the comments section below if installation was also plug and play for you.
Update 11/15/2013: No video? No problem. Click here to see an online Windows 8 driver install guide for AWUS036H from Alfa Network, Inc. Note that this guide pertains to any Realtek RTL8187L based device from Alfa including AWUS036EW, UBDo-gt8, and Tube-U(G).