Does UnityWebRequest completely replace System.Net.WebClient?

I am using a lot of WebRequests (via https) with the System.Net.WebClient class which basically look like this (simplified):

Code (csharp):

1.  
2. try
3. {
4.     result = webclient.DownloadString("someurl");
5. }
6. catch(WebException ex)
7. {
8.     result = HandleWebException(ex);
9. }
10.  

Unfortunately I need to build for WebGL too, where System.Net is not available for obvious reasons.
I am wondering if the new UnityWebRequest can do everything what the System.Net.WebClient can do as well, or are there any restriction?
As far as I understand the UnityWebRequest only runs in the Unity Mainthread so it is probably not possible to start requests in different threads? So only using Coroutines is the way not to have the UI getting stack right?

 

so is noone using it yet? How are you handling multiple webrequests in your game?