Charlie,
on top of the cost, Fruils are no cakewalk either. Cleaning up the castings, drilling out the holes that need cleaning, working with the wire or pins... While they do have a nice weighted appearance, they aren't really any easier to assemble IMO.
Sometimes after a day or so of the glue hardening completely on magic tracks, I will go over the seams one at a time and look for gaps and other places where the glue didn't make full connection on the first application and apply more glue. This is of course done prior to painting and repeated until I feel confident the tracks are solid. I have never had tracks come apart since taking these extra steps, even with repeated enamel washes etc.
Also, they can shrink a bit as they dry. When you apply the glue and it melts the plastic they sort of expand on a very minute level but when multiplied over the link count it's noticeable, especially once it dries as they then shrink back and tighten up a bit. If the kit has the option of a movable rear idler, I always keep that loose until I'm done with the tracks and adjust to fit.