Yes, except the linear polariser on Amazon is about 2-3x the price you'll find for on Ebay.
I've not worked out how many stops I've got with this before the image quality breaks down (which it does quite suddenly if you push the effect too hard)..

2.5 secs, f/16, ISO 100 on a reasonably sunny day - so perhaps 6-8 stops?

1 sec, f/8, ISO 100 - so again 6-8 stops

1/10, f/11, ISO100 - 4 stops or so, just the amount that was needed
Using a VND you set your exposure slightly differently. You choose all your usualy settings (aperture, shutter, ISO) and then adjust the filter to bring the metering to match the values you've chosen. It's a little odd, but you get used to it.