@rischa - I remember distinctly how good the 4349's sounded right out of the box. However, the high frequency compression driver did smooth out in short order as the drivers broke in. I didn't have a very long break in period where the cabinets sounded vastly different, though I put quite a few hours on right away. I run JBL 2269H 18" drivers as subs, so low frequency extension or break in isn't something I could comment on.
As I work for an AV company, my business partner came to audition the system as well and we used a calibrated mic and software to see what was going on in the room. Both of us were very aware of the various graphs that have been published showing that 1.5k dip and we wondered if we could hear that. There is a slight (and very slight) downward curve in the 1800 to 2200 hertz area on the graphs as we measured the room / system, but of the various people that have heard the system (all of them musicians and all of them with very good systems better than mine), no one has stated "hey, what's with the dull / flat vocals" or anything like that. I'm certainly not grabbing for my 1k or 2.5k eq knobs on my preamp and boosting those frequencies. I find these cabinets very enjoyable and have no want to get rid of these for something else.
I have a second system with reasonable components and as I go back and forth between systems, I don't find the 4349's severely lacking in any way.