Soon to be released new Dell Docks may require BIOS and driver updates on your laptop before use!

So no other solution except displaylink adapters? Perhaps the Dell D3100 dock :)

Not true actually, I have the XPS 9550, before I got the new TB15 I was using the D3100 dock.  I can do 3 U2415 monitors( 2HDMI, 1 DP or mDp can't remember)  and my 4K laptop display no problem. 

Right, I forgot about USB expanders. They have own graphics chip and are not driven by the laptop GPU. It is like adding another graphics card, just a very slow one.

You could hook two monitors to TB15, and use its USB ports to drive two of those expanders (or one multi port). Then you'll end up with 5 monitors, 3 driven by internal laptop GPU, and two via USB. The 960M doesn't have own video output, it all goes through Intel GPU and all its display limitations apply.

TurboChris do you connect the D310 to the TB15? Can you drive additional screens from there?

All these USB expanders have displaylink chips on them. I have the Lenovo basic dock at the moment but soon I will need one more screen (4 plus the laptop display) that is why I got the TB15 hoping that it can drive 3 external plus the one on the laptop and with the extender I could drive one more. I do not care about slow as I am running multiple VMs and not graphic intensive apps. (Ok I play Elite dangerous but only one screen :) )

Is there a way to drive the displays through the 960M card which supports more screens? I think not because of the design but that would be nice :) 

This is what I am doing now but I need to get another extender or a multiple one and I was wondering if the D3100 is a good solution for another 2 or 3 screens

I'll add my experiences...

I've got a ~2 month old XPS15-9550 & am awaiting the arrival of my third TB15 dock.  The only thing my dock(s) have done reliably, is charge the battery in the PC.

My setup is a single HD monitor via HDMI, USB keyboard, USB wireless mouse, wired ethernet.  I've applied every update that Dell has that might have even a tangential relation to the dock.  What I've found is that Thunderbolt will disconnect rather reliably if I have a wired ethernet connection to the dock and the WiFi on the XPS enabled, simultaneously.  Of particular note, disabling the WiFi on the XPS results in almost* perfect operation (when docked).  Conversely, with the machine docked and happily running along, enabling WiFi results in near instantaneous failure of all things Thunderbolt (except charging).

I've not sent the first dock back yet.  I've swapped back and forth between the two, and have observed no meaningful difference in performance, reliability, or quirks.  I suspect dell could send me 10 docks and they'd all behave exactly the same as the first 2.

*Almost means that everything works fine, assuming that when you boot the machine you don't get a stuck on a warning screen, displaying a message about an insufficient power adapter, when the BIOS loads.  Odd warning, considering this is advertised as a 240w dock.

As some others have mentioned, I've encountered somewhat erratic behavior with two different USB-C to ethernet adapters.  Sometimes the machine will refuse to recognize the adapter is present.  The first was an Anker, the second a Belkin...with the Belkin seeming to be (unscientifically) the more reliable of the two.  FWIW, both adapters identify as a Realtek USB GbE Controller, same as the ethernet port in the TB15 dock.

After multiple encounters with Dell support, I've got a third dock on the way and suspect I'm no closer to a real solution than I was when I plugged in the first one:/

Holy Computers Batman! I think you've got it!

I have 14 of these XPS 13 laptops and 14 240w docks. None of them worked with the dock when the lid was closed. 4 of them worked with the dock when the lid was open. Only 4 held their connection to an external display regardless if lid was open or close. (I am connecting through the USB-C Port) (Yes I followed all the steps suggested)

I disabled the wireless adapter and magically all my problems went away. Every laptop worked with any external display and it also worked with the dock. With lid open or closed! I notified the Dell engineer whom I am working with and I am now waiting for a reply. Maybe its just a setting that needs changed in the wireless adaptor.

On a side note: I have tested many adapters and I found StarTech works best and we have had good results with Cable Matters as well.  

A few more bits...

I tried using the 3.5mm headset jack on the front of the dock on Sunday for a Google Hangouts call.  Didn't work.  The Dell Audio software gave me a popup message, indicating I had plugged something into the port, but no audio to speaker or from mic.  Plugging into the 'same' connector on the of the XPS itself worked fine.

I purchased a new TP-LINK Archer C7 AC router.  I can now quite reliably use my laptop docked with WiFi at 5GHz (couldn't do that before with a 2.4GHz N connection).  That said, the one Ethernet connection rule still remains when docked.  If I enable the WiFi and have the Ethernet cable plugged into the dock, its all over...instant fail.  Disable the WiFi or unplug the wired Ethernet, and all is well.

Same here.  Just got a WD15 130W adapter.  Did all the updates first as recommended.  Video no problem.  The minute I plugged in the Ethernet cable the network went crazy switching back and forth to the wifi and Ethernet.   Then the second I turned off the wifi in W10 - the problem ended.  I normally do this anyway when I have a docking station - but unfortunate after all this time and people who have identified the issue for Dell - that it is still not resolved.

The other issue I notice with this WD15 and the one I returned is that when I plug in my CAC card (secure card to check my company email) it works the first time but at some point the card reader is no longer recognized.  Plugging directly into the machine is no problem.  Plugging into the WD15 is hit and mostly miss with this peripheral. 

!!!POSSIBLE SOLUTION!!!

Change your WiFi Power Output to 50%. This resolved all my problems with the dock or connecting to any device through the USB-C Port. I do not know how changing the wifi Power Output effects my wifi but so far it seems ok. Please let me know if this works for anyone else.

Did anyone experience similar issue and if yes what was your resolution possible fix. 192.168.l.l