I've not bought the 6th Sense box, but I've used 6th Sense products and I've used another subscription service. Here's what I learned...
6th Sense makes a good product. Their crankbait hardware and paint jobs are above average in their price range. The only issues I've had were cracked bills, but I haven't seen it enough to say it's an issue. My favorite/most used lures are the Crush 50x, Flat 75x, Divine Hybrid Jig and Curve Finesse cranks.
As far as subscriptions go, it's a neat idea. For someone just starting to learn about baits and how to fish different lures it could make sense. I did it for about 6 months, before I stopped. Although I saved a few bucks from retail, I got on average one lure a month that I never used (based on the waters I fish). Basically nullified any savings I was getting.
My personal opinion is I would rather pay retail for the exact lures and colors I want and not leave it to chance. But, if you currently have limited tackle and want to expand your knowledge, but aren't sure how, a monthly subscription could be an answer. My boxes provided information about when/where/how to fish each lure, and suggested rod/reel/line for each presentation.
Hope that is useful toward your decision.