Yes, some of us have tried them. I think not everyone likes them as much as I do. They are certainly not the cheapest option, and I have heard one or two people complain about them not holding zero. Perhaps they didn't mount them properly, or they got bad examples. I got good ones.
I have two of them. I have swapped them around between two No4Mk2s and a No5 and they work as advertised. I can take the scope off with the upper mount (to use the iron sights, which you can leave on, or for easier cleaning of the rifle) and when I put them back on they are still zeroed. If you want these features I don't think anything else is nearly as good as the Cad-Technik, but if you don't care about that, and you want to spend less, there are other mounts that will do the job for less money, though with most you have to remove the rear sight.
The thing I like least about them is what Nelly said, that they put the scope quite high, so you really need something to raise the comb of your stock. I have used a replica of the No.4T cheekpiece, a Beartooth comb-raising kit (neoprene sleeve fits over the buttstock to hold several foam pads of varying thickness to give you a cheekpiece at the desired height - Russells in Calgary sells them) and a commercial aftermarket No4Mk2 target buttstock with full pistol grip. All of these solutions have worked well for me.
I don't know of any retailer in Canada stocking them, but I am sure if you ask around and are willing to pay, someone would get one for you through the proper channels from the U.S. I got mine from American sources, before it was such a hassle. (And no, sorry, I still need them both.) Brownells sells them in the U.S. and I think they are still shipping to Canadian customers, despite the extra paperwork.