You don't really have a clue after reading the long list of features. But it is a must have.
It can be installed directly via the Homebrew Browser (an app on Homebrew channel). So you don't need to do anything like touching the SD card. I installed it after I installed USB Loader. It works without a hitch. I suppose it will work without the USB Loader. I have everything compatible to Wii 4.3.
Now that you need the USB drive to be at the Wii to backup all the games, you don't want to move the drive upstairs and downstairs to the PC and the Wii. Two separate drives aren't necessary better even if you have the money. You need something to connect your PC to the USB drive at the Wii.
The Wii is a pretty good SDHC card reader (and writer). You can watch your pictures and videos right on the big screen after a trip. If you can copy the card to your PC, you don't need a separate card reader.
The WiiXplorer is basically a GUI file manager, like that of any other OS. It's behavior like Windows Explorers and nautilus(?) in Ubuntu. Basically that's the tasks you do daily the most, copy, move, delete, rename files and folders.
The multi device means the SD card drive, USB drive, and SMB share on the PC over WiFi is supported. It should also support USB flash drive, but I didn't tried.
There is an icon at the top left hand corner to show what device is
being displayed. If you click on it, there's choice of SD, USB, and SMB
The USB drive connected to the Wii is NTFS formatted (Windows). My desktop is of course ext (Linux), but wrapped up with SMB.
It's the same SMB setup as mplayer-ce. But you can do it via the GUI when you run WiiXplorer. Remember to uncheck readonly at the PC end if you want to be able to write back to the PC drives.
So you can copy/move files from any device to any device. And you can sit at the Wii and do everything with the Wiimote, without going to your PC, as long as it is on for the SMB server.
If you download something to the PC into the SMB share folder, you can move it to any storage on the Wii. You can also move anything on the Wii storages into your PC. With this thing, you never need to go up and down stairs to install something.
But moving files over WiFi is pretty slow if you have 4GB of data. The speed is about 500 MB/s. You need 2000 sec to move 1GB of data. It's not too bad. If you want it immediately, you can carry the USB drive around, the speed is at least 20MB/s at the lower end. Otherwise you can start moving something when you are not using the Wii for an hour or two.
If you setup the Wii as an ftp server, you can sit at the computer and do everything too.
WiiXplorer also launch installed Homebrew applications according the file type. But it didn't work for me. If the image display works, then it's a compliment to mplayer-ce.
Usng WiiXplorer is obvious, except that the right click on a file is achieved via the + button. You use this button to bring up the copy-paste menu.