Well I dont own one, but I have driven one multiple times.
I think for a budget booster, it's a good buy. Low enough torque that your ATX should be able to handle it without issue. IMO it's the cheapest long term solution for more power and it's very reliable.
But the downside to the JRSC is it's upgradeability. Take a look at what Ray at McNews has done with the big boost, and that's really your "safe" daily driver limit. I mean there might be more power there, but I think it will be at the cost of reliability.
If you truly to plan on replacing the ATX, and your long term goal is "big" power, then dont get the JRSC. It's gonna cost you tons of money to get it where you want to go. I'm not speaking from my own perspective, but from reading countless other threads where guys have found out that the JRSC just costs to much money and work to get up to the high power numbers they want. But for a budget booster who will be happy with lesser power, it's a great choice if that helps.