What are the best Room Accustic Treaments members have found?

It depends what you want...
I worked with vicoustic and submitted a project to them, they came back with 3d renderings and room modes analysis and treatment suggestions.
I believe other companies offer similar services.
I used diffusers and absobers, mainly on reflective points and it brought a sense of ease to the music. I didn't go all the way because I didn't want to turn my living room into a mastering studio.
If you want something even more aesthetic, I would look at artnovion.
They have some good looking products.
Others mentionned GIK, it's also good.

ieales516 posts12-05-2019 2:04am" Books, shelves, art & carpets.

But then, I spent a few decades in sound studios, so I'm probably odd man out here. "

This must be basic. No audiophile should ever put up big pictures with reflecting glass-fronts. We need to be aware of the impact a leather sofa has in the room versus a velour sofa or chair. Know that real paintings made on canvas are wery efficient diffractors and will eat flutter-echo. Decorative wooden blinds are actually adjustable diffractors and will calm down big windows or mybe a wall. Avoid naked corners, try to brake them up with something. I have a big plastic tree in one of mine, next to a classic painting with a matching motive. Females looks at this and give me an appreciative look. If they only knew..

One thing I can say without fear of contradiction that does not (rpt not) work is SONEX foam panels. You know what I’m talking about, those sculpted dark gray open cell foam 2x2 panels that are ubiquitous in control rooms and recording studios. SONEX foam and similar products, even foam filled chairs like the IKEA POANG chair, have to be one of the worst sounding materials ever foisted on naive and gullible audiophiles. Even a little bit in the room makes the sound unnatural, phasey and wooly.

+1 for Primacoustic panels. Purchased mine from Sweetwater Sound. Placed them on all four walls plus the ceiling at all first reflection points. Enormous improvement in SQ. More than any gear change. Remember, the room and the setup determines at least half of what you'll hear. 
Also +1 for Jim Smith's book Get Better Sound.

+1 for avoiding a foam solution. It does not work evenly over all frequencies and is also a fire hazard. The best engineered panels are made of 6lb per cubic foot fiberglass. The way they work is that the acoustic energy hits the fiberglass causing the fibers to vibrate. The fibers vibrating against the air causes friction with the air turning the acoustic energy into heat... Something like a millionth of a degree or less... 

Fiberglass panels typically keep their shape with an acoustically transparent covering and a resin frame. 

Acoustic diffusers work great for diffusing the sound but do little to absorb excessive acoustic energy in a room. Furniture, rugs and carpeting can help absorb excessive acoustic energy in a room. But the problem is how much and what frequencies. Well engineered acoustic panels can help control a room in equal increments. Have a softDr room? Try 15% treatment. Have a hard room? Try more treatment but keep it to a max of 30% or risk making the room dead or dark... Unless, of course, dead or dark is your purpose or pleasure. Forensic labs might use a 50% treatment of 2" panels.