Im using this since it was zPoolminer.
Essentially its a really simplified tool to get into mining. It uses pools like zpool or zergpool and switches to the most profitable algorithm automatically.
What is really nice, especially for new miners, is that you can add custom coins. So as long as new coins dont use any new algo, you can just put in all the needed values (wallet, pool, algo) and start mining, without creating tons of batch files.

And if you dont have time to look for new coins, there is also the coins called "admin coins", which are updated frequently.

With the website all your settings also get stored, so you can easily copy them to multiple rigs or restore them in case something happens.

In the end of the day it just makes everything easier and more accesible. oh, and did i mention that the devs listen to your feature requests really carefully? thats actually the thing i like the most