Well if transparency, attack, along with warmer less pinched harmonics are real rules in audio, than that is what you can gain going with a GOOD crossoverless speaker systems, but not all even if they claim this can do it in the real world...
I owned Dynaudio, Jm labs, and klipsch, along with some Custom 7 ft line arrays before my current speakers which are crossoverless.
The top of the Highs, and the bottom of the lows are always an issue when going into any single driver Full range crossoverless speaker. Mostly these designs are best known for fast, articulate, full midband and voicing, kinda how Cardas Cables, and Tubes get their reputations.
A few ways to correct frequency extension of these designs at the top and bottom is of course to either horn load them, or come up with some specialized boxes to more standard vented, or sealed cabinets to still get resonable response out of them, or build around the FRD with very fast subwoofers and/or supertweeter systems to integrate and extend the sound further.
Bottom line is that you can find some FRD Crossoverless systems that will blow your doors off and you will not go back, or some that are pretty normal just like most dynamic drive tiered crossover systems (3 way, 2 way, etc..) And this finally comes down to money, yes the best ones will cost quite a bit more money, but the used market has some pretty cool designs that don't cost a fortune to get your feet wet, such as the Zu Druid, or the Omega speaker lines, but if you want no holds barred than they will cost substantially more money...
A new one that I know is coming out soon is the Zu Audio Presence at 6 k a pair if that helps you out. In theory that should approch 90 or 95% of the best Crossoverless speakers can offer, however it is augmented by dual 10" woofers on an Active crossover amplifier, and a supertweeter for the super airy extended highs.