Pros: They have that orthodynamic magic taken to the next level.
Cons: The magic comes at a heavy price.
If there is a more apt example of the Law of Diminishing Returns than these headphones, I'd be surprised. For the refinement over the LCD-2s, the price is double. With the new LOTUS drivers, an acronym that appears to target electrostats ("Light Omega Type") there is a significant improvement in all the areas that the LCD-2s had issues. Complex orchestral music is now no longer a blur; the mildly annoying ringing in the treble has gone and everything sounds more detailed and separate. It is easier to pick out individual instruments in good recordings. The penalty is fast-attack fun of listening to, say, well-recorded pop has been replaced somewhat with a more "analytical" presentation that picks the nits out of recordings and equipment, as now the rest of each note is now more detailed, revealing the texture in a manner that previously was the realm of electrostatic drivers.
The improvements are also of only a degree that they might not be readily noticeable on other than high-end gear, so I'd say if someone had a total rig budget, if getting the LCD-3s was going to result in a significant sacrifice in source and amp quality, I wouldn't bother.
As for the price, lets face it, audio is an expensive hobby to get serious about. If you want to be positive, Sony R-10s, now a decade out of production, cost over $5k on the used market. Even the Stax SR-009s cost around $5000 or more outside of Japan. However, the Stax do still best the orthos for ultimate detail, imaging and being the closest to having a lack of coloration, but less than before.
In the end, I could live with these as the One Headphone at home. That being said, I can only wish this technology would filter down into lower-end headphones. Those who have experienced the inexpensive magic of vintage orthos know that great-sounding headphones don't have to be anywhere near as expensive. LIke other top-of-the-line headphones, the LCD-3s may be a huge win for those who can justify shelling out for them and comparable equipment to get the most from them, it will be how they influence mainstream manufacturers that will end up mattering the most.