SnailUI is a pixel perfect UI, meaning everything is aligned perfectly. SnailUI skins almost everything, including the minimap, action bar, casting bars, etc. SnailUI is currently in a beta state, so there are probably plenty of bugs to be found. I would appreciate it if you reported them in the comments or through Twitter.
A lot of aspects of SnailUI can be changed via the in game interface options (or by typing /SUI or /SnailUI) or via the lua files themselves. This UI is also using Tuk's warlock bars addon as a temporary fix until oUF is updated. Should you need to contact me, I can be found via Twitter. (@1Snail)
You can also stay up to date with the cutting edge versions of SnailUI by visiting its GitHub repository here: https://github.com/1Snail/SnailUI (The files here can change many times a day so it's not recommended to use this version of SnailUI unless you know what you are doing)
Read: SnailUI relies on both oUF and oUF_SpellRange, so make sure that these 2 addons are installed before continuing. To install SnailUI, just unzip the SnailUI folder into your World of Warcraft / Interface / Addons folder and you are good to go.