In order to test the throughput of the router, I used netcat to transfer a 4.5 GB file. My laptop was on the wireless and the test machine was on the router's wired network. The wireless to wireless was done using my desktop and the laptop.
Wireless to wired: ~4000 Kbps average
Wired to wireless: ~10100 Kbps average
Wired to wired: ~15000 Kbps average
Wireless to wireless: ~3500 Kbps average
I'm disappointed by the signal quality. I determined the quality of the link using the Ralink Wireless Utility included with RaLink's drivers. I averaged a 55% link quality at a signal strength of 52% with 50% noise while associated with the WL-500W. This measurement was taken at about 15 feet from the router with one wall between the router and the laptop.
I tried two of the devices additional features, the print server and the file server.
The print server setup was easy with my Samsung ML-2010 laser printer. The printer was recognized and usable by the WL-500W. Installing the printer in Windows is not terribly easy, and there's no instructions included in the router's interface-I had to consult the manual. It works, and that's the big thing.
The file server requires that your drive be formatted FAT32 or EXT2. Windows can't do EXT2 natively, so you're stuck with FAT32, and multiple partitions if your drive is larger than the 137 GB barrier of FAT32. When you connect a drive for the first time, the WL-500W writes a bunch of miscellaneous files and folders to it in preparation for download manager use, including the device's swap file that it needs in order to run everything that will be used for the download manager.
It shares the files using Samba (Windows shares) and FTP. I would have liked to have seen more options, like WebDAV or NFS, but there's limited space on the router's memory for extra, geeky things like those.
You can limit the shares to specific users, which may be advantageous if you want to use the WL-500W's connected drive as a home network backup storage for multiple people, possibly on multiple computers.
The download manager works, but is a bit of a pain to install. I don't want to have to install anything! Having to install things limits the number of people, places, and operating systems that can use the Download Manager functionality of the WL-500W. A web-based interface to the BitTorrent client and HTTP/FTP downloader would be far more appropriate. If there's not enough room on the firmware itself, the router could download and unpack things from ASUS's web site.