I went to Deja Vu this weekend and heard the big horn system that they brought to the show in a bigger and better-suited room. In this setup it sounded substantially better than it did at the show. I noticed that it does not sound quite as good when the system is turned on than when it has warmed up a bit; apparently, the field coil drivers and/or the tungar power supply need to warm up a bit before the system sounds it's best (bass is boomy and ill-defined until the system warms up).
I was particularly struck by how good the 597 tweeter sounds--the system was very airy and open sounding without even a hit of harshness; this was the smoothest top end I've heard and it was so well integrated it was like there was no tweeter present, but, the sound was not lacking in high frequencies. The 555 midrange had the smoothness I would expect from this driver, but, the G.I.P. replicas also delivered the kind of detail that made it sound more like a Western Electric 713B driver than other 555's I've heard (a VERY good thing).
The bass on the system is not quite what I would find ideal, but, this is always the case until the system is specifically tuned to a particular room, system and personal taste.