So I've had the chance to try out Unity Hub for a while, and had ups where I completely switched to it, and then downs where I finally got rid of it.   

When you start Unity, you get the project selection screen.  (Unless you chose to have it auto start on your previous project) Hub is a separate application to replace that screen.  It adds new features, like

• Multiple versions of Unity
• Assigning projects to start with specific install versions
• Right clicking on an install version and having it add a new build target (without all the UI's to monitor)

It worked great initially.  So much so that I uninstalled Unity from the machine (because bug #1, it doesn't recognize existing Unity installations.  it seems like they *have* to be under a specific path/format.  It says you can select existing ones, but it never recognized the version I have) an let it install Unity for me.  Next I also installed the Beta, because it was easy.  It seems far faster to install through Hub, than via download/direct install.

I loved this feature. 

But then some problems started in...

• Some of the features like Android install, I could not get to work after.  It took a lot of extra steps to resolve, steps I don't recall having to go through on my normal version.  For instance, it could not pick up the JDK install path on its own.  
• It can't install older versions, like 5.6.  Which seems a huge reason for supporting this.  There where huge transformational changes between 5.6 and 2017.  Some projects just needed 5.6.  It seemed like this was the key reason to have Hub, so I could go back easily.
• I already had Visual Studio Enterprise installed on my system, and it couldn't register it.  Well not during the install anyway.  I had to go in, and find it by path, but then it didn't have any of the Unity properties installed for Visual Studio. 

Ultimately, I ended up uninstalling it, and going back to the base installation of 2017.Latest and VS Enterprise Latest to get everything happy again.  I intend to try Unity Hub again, but will wait until its out of beta.

Check it out / download it here: https://blogs.unity3d.com/2018/01/24/streamline-your-workflow-introducing-unity-hub-beta/

If your needs don't step on those issues, like android or needing to jump back to 5.6, I think its a great product.