I wanted to cross post my experience with my XPS 13, and how I seem to have gotten wireless working like I expected it to work in the first place:
YMMV - I was having some serious wifi issues while traveling, so I decided to try and take matters into my own hands to get a solid connection as I have other work to do, other than constantly reconnecting my wireless adapter.
I have an XPS 13, but it does pack the same Advanced-N 6235 adapter. I'd read a thread somewhere else where someone utilized the Windows 7 driver from Intel with marked success. It was better than the latest Windows 8 driver, but it was still pretty awful. Realizing there were other drivers defined in the zip I downloaded, I decided I'd try a few to see if I could find one that was stable. I seem to have done just that.
Here's what I did:
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I installed the Intel(R) Centrino(R) Advanced-N 6205 driver instead. Driver Version: 15.3.1.2. Available from the Intel website.
downloadcenter.intel.com/Detail_Desc.aspx*&DownloadType=Software%20Applications
Download the zip appropriate to your OS:
Windows 7 32-bit: Wireless_15.3.1_Ds32.zip
Windows 7/8 x64: Wireless_15.3.1_Ds64.zip
Extract the files somewhere you can find them easily. Once extracted, its time to "update" your driver.
Open Device Manager, or otherwise pull up the properties for your NIC. A way that should work for just about anyone, Win7 or Win8:
Windows Key + R (in Desktop for Win8)
Type "ncpa.cpl" and press the enter key
Right click your WiFi adapter and select "Properties"
Click the "Configure" button"
With the properties of your network adapter up:
Click "Driver" tab
Click "Update Driver" button
Choose "Browse my computer for driver software"
Choose "Let me pick from a list of device drivers on my computer"
Click "Have Disk"
Click "Browse"
Browse to the files you extracted earlier. Drill all the way down to the "Drivers" folder, and select one of the .inf files
Click "Open"
Click "OK" on the "Install From Disk" dialog
Click the check box for "Show compatible hardware" to clear the check, and give you a list of all the drivers in that folder
Select "Intel(R) Centrino(R) Advanced-N 6205"
Click "Next"
Click "Yes" on the "Update Driver Warning" dialog
Once the driver has finished installing, connect to your access point/router/etc, and see if your speeds are any better. The difference was VERY pronounced for me. I haven't had a chance to burn it in more than this evening, but so far it's worlds apart. Word from the wise - The 6230 driver has similar performance, but it ramped my CPU up to 99% until I unloaded it.
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If you try this (at your own risk, of course), sound off on your results so this can get as much attention as possible, and hopefully we can get a better driver for this 6235. With my current experiences, I'm very certain that this is a driver related issue, and not hardware. While I may not work on client hardware for a living, I think this should be the nail in the coffin as far as if it's hardware or software related. :)