I have been doing some research and found some guys using them on the street and in desert racing aplications. The baja one fron deaver is based off a 5/8 hiem joint from a shock and is linited to 18* and i think the best route.The johnny joint has more fles 36* or 48* iirc this is where problems could happen to much flex but people are using them.It apears all say it helps ride quality as the spring is no longer in a bind with a bushing but it does add a little body roll. From all i have read said it is not dangerous and only slightly noticable could be also that with the spring no longer bound up by the bushing it just flex's easier and therfore more body roll. The johnny joint is rebuidable more easier and cheaper than the baja joint is more expensive to rebuild.
baja joint is $160 a pair.