So, I ordered this as sort of a test of Tindie (my first purchase) as well as supporting a Hackaday.io project. Now after running with the product installed on my printer for over a week, I've become forced to write a glowing review. I normally don't take time from my busy life to review things unless they're horrendous or amazing. This is definitely one of the latter.

The things that stand out to me are:
1. Documentation - the writeup on Hackaday.io is detailed and documented well with pictures. The only thing I would change about it is to add a diagram showing how to connect to your 3d printer's controller - but really it isn't any different than your old heated bed. Also, with the SSR chosen, you can do PID just like the old DC heated bed you probably used.
2. Safety - the little things like including a cover for over the SMD LEDs and the thermal fuse, copious heat shrink, in-line fuse, etc. These all add up to a well thought-out product with safety not taking a back seat to convenience or cost.
3. Cost - what you get for what you pay is well worth it. The SSR itself is not cheap and is a good brand. Nothing was sacrificed in the name of making money - rather I'm actually very surprised that this product can sell for what it is and the maker actually feels it is worth his time to produce!
4. Community - on top of it all, I would have bought it to support Hackaday and Tindie and the maker - if for no other reason than to help support another maker and not to support some large corp.

Thank you! I hope you're still selling these when I make my next printer and need another! Consider creating a circular heated bed as well for the delta people out there? That might be my next build.. :-)