I have some, but I haven't used them yet.  I decided to cut gaps instead of using the insulated joiners, but breaking so many jeweler's saw blades has caused me to rethink if I'll use them or not.  I won't be home for a couple more days, but when I get there I'll try to remember to test them out.

Not answering the posters actual question.. but to address Dave's issue..

My friends who have large N scale model railroads use a thin cut-off disk on a dremel with one of those 90 degree adapters. They actually use a knock off brand.

I didnt do this only because I didnt have one at the time. I will never use a razor saw to cut gaps again.

I used both insulated joiners (Peco, to match the funky code 55 profile) and gaps on my little layout. I much preferred gaps. I filled them with styrene, used gap filing CA, and cut and sanded them to shape. Pretty much invisible after track painting.

Chris