3D Performance could be better, and a bit more comfortable. BenQ has newer glasses, that were provided with my review projector, however, I am told that the W1500 projector, at least here in the US, does not come with any 3D glasses included. Those newer glasses were still in the upper 40 gram range, with some competitors offering 3D glasses that are 20-40% lighter. The good news is that some of those are "3rd party" glasses that you can buy to use with the W1500.
Brightness on 3D is pretty darn good, there are some Epson's and Panasonic's near the price that are definitely brighter when doing 3D, but understand, not drastically so.
My primary complaint is that BenQ is still using DLP-Link glasses. Many (most) manufacturers seem to be moving to RF glasses. When viewing 3D, on very dark scenes, I sometimes notice that black seems to be slightly red, and that's the DLP-Link, I've seen that many times before. It's mostly subtle, but a flaw, when you do notice.
That said, crosstalk is basically nonexistent, unless it's coming from the source material or the source players themselves. No apparent crosstalk is a real plus!
That said, I'll cross my fingers that BenQ abandons DLP-Link in their next gen projectors, as I have found non-DLP link glasses (when an option for a projector with DLP-Link) to be slightly brighter, produce a slightly more dynamic image and do better on black levels (no red).
Bottom line on 3D on the W1500 projector: 3D is a lot of fun, but most will find (using a typical screen in a darkened area), to be a bit thin on brightness if you try to push out past about 110" diagonal. I still find 3D to be less accurate color wise, and suffer some other issues, so I don't try to judge 3D performance anywhere near as critically as I treat the 2D image!