A lobbing error is really an out of phase cancellation that occurs off axis. With the X-CS or any other side lay MTM used as a center channel there is this effect. If you move far enough off axis then one woofer is delayed in time (one further back from the other) and becomes out of phase with the other one.
The further the woofers are apart the worse this gets. The X-CS allows the woofers to mount over the face plate of the tweeter moving the acoustic centers as close in as possible to minimize this effect.
With the X-CS you are good to about 20 degrees off axis. After that you will start to see a slight dip in response in the 900Hz range.
I am not sure what to think of the review you guys posted a link to. It is a bit discouraging to spend so much time designing a very high quality speaker only to have it reviewed using a cheap home theater receiver and DVD player.
Most of his imaging observations are completely related to his electronics and positioning. Silver interconnects with that gear sounds scary to me. No wonder he had issues with the highs. Trust me there are no issues with the highs at high volumes or any loose of control.
I heard a pair of X-LS's this past week end at Gary Dodd's house (Dodd Audio). He played the hell out of them with 150 watt tube mono-blocks and played them so hard that the curtains 2 feet behind them were dancing hard from the air blowing from the ports. The highs were smooth as glass and held up with ease. There was zero congestion or compression. In front of the tube amps was one of the best pre-amps ever made and a modified DAC-60 DA converter being feed info from a CEC transport. It was top notch gear. It is the kind or gear that should be used to make do a review. Regardless of the price point of any item being reviewed, you should never bottle neck it with entry level crap. This will not allow you to know the true capabilities but more of the limitations of the upstream components.
On the contrary the similarly priced Paradigm or Axiom speakers aren't even close. I guarantee you that the X-LS will beat the paints off of them. They can even be taken a step or two further with a few minor tweaks. See thread on inexpensive upgrades here:
http://www.av123forum.com/showthread.php?s=&threadid=15371
Hey, don't take my word for it. Try them out. You can return them if you don't like them.