Never heard of it but it sounds similar to Passport America which is very popular and has been around a long time.
Yes, you'll get 50% off but you need to read carefully because it can have day restrictions or how long you can stay at that price.
We used Passport America as a fill-in as we traveled and it worked very well. It's cheap enough per year membership and with just a couple stays you have paid off the cost.
If you're considering something like this I'd go with Passport America who is a stable company.