Speakers least affected by room acoustics

Yes all good points made. The Lyngdorf 2170 does wonders in my room with high ceilings. It does in fact help!

The advice that most mirrors my experience comes from audiotroy.   If someone come to me asking me to build a speaker for them and they had a lot of boundry room issues.  I would have recommended one of two.  One was nailed above.  An MTM with a rug covering as much of the floor possible in front of the speakers.  Next alternative would be a speaker with a wide front baffle.  
When we build speakers, we use Baffle step compensation to counteract the effects of the sound that shoots around the cabinet.  The wider the cabinet front the less or no compensation is needed.  With a wide front baffle,  it helps keep all drivers firing in the direction the speaker is facing and stops midrange reflections. Still add the rug to the floor to help floor reflections. I then would add to get a sealed box woofer or a front firing port in this case.  Drape as much of the rear wall as possible.  You should be able to pull in some fairly solid results. 

corner loaded speakers like audio note or klipsch can work well with most any room provided it is big enough and you have the freedom to make it work with respect to room layout and furnishings.  

The living rooms (my main listening rooms) in both my previous house and my current house have very high ceilings - 16 feet. I did not have a ceiling echo in either room. The current room is 24 x 14 with speakers on the long wall. All hard surfaces with parallel walls, ceilings, and floors and no treatments - not even an area rug. If I were you, I would speak to a couple of manufacturers such as Sean from Zu and Duke from Audiokinesis.

There are things one can do to "treat" a room that is compatible with normal room decor.  As Shadorne mentioned, start with a thick carpet, or at least a large rug.  This will reduce the slap echo of sound bouncing back and forth between the ceiling and the floor.  If you have a lot of bare walls, put a decorative wall hanging or oriental carpet on the walls.  Book cases or anything else along the wall will also act to break up reflections.

Listening in the nearfield also helps to reduce the effect of the room because a higher percentage of the sound you hear will be coming directly from the speaker.  This requires that the speaker be reasonably balanced for such listening (speakers sound much brighter when listening close up, so not too bright speakers will help).

The use of tall dipole speakers is also a good idea if you can meet the requirement of locating the speaker well off the back wall (about 4 feet or more is needed).  The height of such speakers means they do not radiate as much energy upward, and because they are dipoles, the front and back signals are out of phase and tend to cancel at the sides; the sound is more concentrated within the area between the speakers.

In rooms that are really challenging, and where placement options are limited, a speaker designed to be very flexible in placement can be a big plus.  For example, I've heard Gradient Revolutions used in some really difficult situations and they sounded quite good.

No matter how bad a room seems to be, there are usually setups that will work.  The challenge is finding them.  It can take quite a bit of experimentation and patience to find the right spot.  This is particularly the case because moving one speaker one inch can make a big difference if the speaker is sitting in or near a node (a place where major reflections are either reinforcing or cancelling a frequency).  I would suggest googling the "Sumiko Method" of speaker setup; it is quite useful with tricky rooms.

Good luck.