Well it allows for castor adjustment, but generally standard castor is spot on. However (brake) judder often is caused by the (poly)bushes (the tca and arb) Now with a adjustable tca and compression strut, it is simply not possible due the rose joints. And your wheel allignment is spot on because bushes allow the wheels to be moved in differnt directions, which causes wrong wheel allignment. (less grip, and tyre wear)
Cons can be: Besides the investment it also will transfer rolling sound from the tyres to chassis much more than dampend by the bushes.

Rinus

btw, i'm also interesed but prefer a compresionstrut kit with a (adjustable)arb.
Or can i relocate the original arb just above it's standard location, chop of the tca ends, and clamp it to the compression struts? (rs1600i style)