16 is OK I think for a ultrabook.

My goal is to have a 16 GB ultrabook for when away from my desk, and a 64 GB workstation when at my desk.

I always try to find the beefy laptop to replace both, but I am never that happy in either place. Too heavy for the road, too slow for the desk. Been trying for like 10 years, and sad every time at the laptop I end up with.

* In theory the CPU in the XPS-13 supports 32 GB says Intel, but I have never seen a true Ultrabook with 32 GB. Which is a bit sad of course...

I have had 32 GB in my (i7) W530 since I got it (about four years ago) and I'm almost positive it's not DDR4, although I'd have to check to be certain.

Interesting, it is 32GB of DDR3. That is the only one I know of so far, so I guess it may be time to start comparing chipsets.

As an owner of the 13 and the 15, yes. The 13 has a ULV i7 with <=16GB. But the 15 has a full i7 and goes to 32.