I use it on NAND Emulation and it works great on my wiiware games. I don't have a lot but the ones that I have, work with no issues. For me, where it really shines is loading games off of hard drive using it's NANDEmulation. I can also load DLCs which is great for music games!
NANDEmu and Uniiloader come with guide text file. NANDEmu is pretty straight forward. It's like SNEEK. You need to put some files on the SD or USB (whichever device you need to use), then copy your virtual NAND files. You can even use the virtual NAND files from your SNEEK. The Uniloader is a channel that you install on your virtual NAND and can load Homebrew channels, WiiWare/Virtual Console games, wbfs games and even system channels (Mii, Internet, News, etc). You can even use Uniiloader inside SNEEK and load up your games from there!
To use virtual NAND, you will need a NAND Emulator and a NAND Image. For starter, I recommend SNEEK for NAND Emulation. You can use ModMii to get SNEEK and also a NAND Image, see the sticky in the main forum. If you're going to use SD, get the SNEEK, if USB get UNEEK. For NAND Image, get the System Menu version and region that works for your set up, I'm using system menu 4.2. When you set up the NAND Image, there is an option to get other channels, I recommend to also get Wii Shop Channel and Mii Channels but they are optional in case your games need them.
Once you have the SNEEK and NAND Image working, use ShowMiiWads to install your WiiWare/Virtual Console games into the NAND Image. You can also use ShowMiiWads to install Uniiloader to the NAND Image.
Now, put your SD and/or USB device (whichever you set up for NAND Emulation) in the Wii console, boot up BootMii (via Homebrew Channel by pressing "Home" on the WiiRemote and choose "Launch BootMii). If this is your first time booting up your NAND Emulation, it might take a while to see the System Menu, 3-5 minutes, depending on the speed of SD or USB. Once the virtual System Menu is loaded, you should see your games and Uniiloader. Launch Uniiloader and you should see all your installed games and launch them inside Uniiloader.