I myself have been saving for a while to purchase the PSE TAC-15, a crossbow upper that fits to one of my AR lowers. I shot one at the range a while back a few different times and liked it's accuracy, power and quietness. The crossbow and the bolts themselves are a little bit pricey, so gonna have to be careful with them rascals.
Any intel I have learned about their functions, operation and performance has been gained from the internet, reviews, product reps, Gun Shows, owners of the bow itself, and my limited hands on range experiences...and I liked it.
I got people here as you can see, that can help me out too!
I feel informed enough, and my exposure with the product convinces me that I feel I need one. When I finally have one, that's when the fun begins.