Soundlabs are excellent speakers. U-1s, A-1s, and M-1s are all among the most impressive speakers available - if you have the right equipment, and if you have a proper room.
I've heard at least seven pair of Soundlabs: 3 pair of U-1s, 2 pair of A-1s, a pair of M-2s, and a pair of Pristine IIIs. One pair of U-1s sounded exquisite, most of the rest sounded very good, and one pair sounded very so-so. I don't think the difference was so much attributable to the models (although, no doubt the U-1s are the best of the best), or even the electronics (although the gear, especially the amps used with Soundlabs will make a significant impact). What I believe caused the considerable differences I heard among the seven pair was the variation in room acoustics.
At the end of the day, the low end that you can get from Soundlabs, or any other planar, or any speaker of any design will to a degree be determined by the length of your room. For example, I think a 32 Hz signal has a wavelength of approximately 35 feet. That means that if you are trying to accurately reproduce a 32 Hz signal, your speakers need to be at least 35 feet from the back wall (behind the listener) and you will need some additional space between speakers and the front wall (behind the speakers). With less than that total distance, the primary wave is going to reflect off the back wall before it has fully "unfolded" it's fundamental wave and you are going to have less than an ideal result. How much less than ideal is going to be a function of several considerations, only one of which is the length of the room. Once you establish the room length needed to support your desired lowest frequency (assuming the speaker can go that low - pretty much all models of Soundlabs will go to 32Hz), the room length will in turn dictate an optimum room width and ceiling height. (While there is some debate about whether Cardas' formula yields the exactly optimum "golden ratio" it appears that most of the other ratios put forward as "golden" are substantially similar to the ratio recommended by Cardas; ie, the relationships between room length, width, and height are widely accepted as being important to achieving good acoustics.) Additionally, the ideal room will not be rectangular in shape, but will have pied out walls and a pied ceiling (all of which starts to resemble the shape of a concert hall). Finally, the room treatments need to be implemented so that reflections and absorptions occur at the appropriate locations. The chances of all this lining up in a room that wasn't designed for audio is slim, and therefore what virtually all audiophiles get is something that is less than optimum. How much less than optimum is generally unknown until you experience the environment (ie, hear the speakers and the rest of the system in the particular room). It may be that a given room happens to yield acceptable results, or that in moving up from a lesser set of speakers to say, Soundlabs, that the improvement is enough to meet your expectations. But I'd be careful about saying that any speaker is notably less sensitive to room acoustics than any other speaker because all speakers interact with the room to form a "system" that impacts the overall sound.
I know that the readers on this thread probably know all this stuff, but I can tell you that once you invest several thousand dollars in a pair of fairly esoteric (expensive, large, heavy, hard to pack and hard to ship) speakers you won't want to find out that what generally might have worked for someone else doesn't work so well in your room. It's my opinion that when you reach a certain level of equipment that attributes such as frequency extension (at the bottom and top), frequency response/tonal balance, defintion/detail, and imaging are all going to be impacted as much or more by the room as they will be by the equipment.
Again, I think Soundlabs are among the all-time great speakers, but I know from experience that you can't just stick them in any room and expect them to do their magic. As much as I admire Soundlabs, I can't see any big technical reasons (other than perhaps their dispersion characteristics) that would make them easier to place in a room than other planars. And even with respect to dispersion, I think all you can say is that Soundlabs have a different/unique dispersion ability, but again, whether that ability works well in any given room is a function of the room's characteristics and how those characteristics work with the speakers its not just a function of the speakers.
In summary, I think it's wise to proceed with caution on generalizations. With so many interdependent variables I think the results are as likely to be random as they are predictable. Having said all that, Ill go way out on a limb and say this if I had a free pass on just one of the variables, I think it would be room length; having a longer room (well over 20 feet and preferably closer to 40 feet, or even longer) would likely give the low end a chance to do its magic, and in turn get out of the way of the exquisite midrange and high end that Soundlabs can reproduce. Additionally, given that most folks building rooms in houses have some sense of proportions, any room that is 40 feet long is likely to have some decent width and probably ceiling height although the chances of the ratio being golden is slim (obviously a 40 foot hallway isn't going to do the trick). To be sure, this "longer is better" notion is just a consideration and is itself random and far from quantifiably optimum, but I think the beauty of Agon is that people are helping other people learn from their experience and as a result hopefully more people are getting a reasonable return on their (money, time, and effort) investments. With that as a caveat, my very rough rule of thumb is that under 20 feet in length, you are pushing your luck, at 20-30 feet you stand a chance, over 30 feet youre getting warm, and by 40 feet you might be hot. And if you really want to get it right, study, measure and try to create the ideal room environment, or try to get a demo in your room first (good luck with that :).
