All ADATs will sync together with the serial sync cables properly attached. Tape-based ADATs will sync with the hard-disk HD24 as well. The blackfaces wind/rewind time is much, much slower than an XT or XT20, if sync'd to a newer machine, give it time to sync and lock. Also, if you're using mixed ADATs sync'd together, remember to not switch the tapes from one unit to another. Use the same tape in the same machine each time. Remember that blackface ADATs record in inverted phase on the tape... it's corrected on playback. XT and XT20's don't do this.
People slam them all the time, but I think ADATs are great!