This is one subject that I don't agree with Alan.
They don't have to be big/ugly, and they do work, in my opinion if you use the correct proven material. And no, it was not just my brain getting used to the sound. If placed correctly, the sound is far less skewed and there is less ringing and echoing.
I'm a supporter of bass traps and FRZ (first reflection zone) panels. I'm also a supporter of multiple subs. Bass collects in corners of rooms, including floor/wall and ceiling/wall locations, which affects the FR throughout the entire room. The bass traps DO help even out the frequency response for all locations, just like multiple subs do, they can work togethor in harmony. I will say I am not a EQ fan, and plan to sell my SMS-1 soon.
This science applies not only to recording studios, but also to home applications. Engineers would not use them in recording lab settings if there was no benefit. Graphs don't lie either, and they don't have to be expensive. I made all mine myself, it was very affordable and easy. If your not a DIY person, GIK and others are very affordable as well. Other companies can be more expensive.
I've had a few auditions in my home, the last one just last week. The person mentioned how tight/accurate and not skewed the sound was. This was not the case with bare reflective walls. Yes, before the Axioms sounded awesome, but a person could notice the echo or reflective sound bouncing off the side walls and ceiling.
I am not advocating completely covering every square inch of wall and ceiling space, as to much can deaden the sound and you do need a little reflection. If you've ever gone from having a reflective floor (concrete/wood) to placing a pad/carpet/ it is like night and day better. The same applies to FRZ's on walls and ceiling.
Here is a great read on the subject.http://www.ethanwiner.com/acoustics.html
Here is a before/after graph of my room with measurements taken in 1Hz increments. The only change was adding front corner bass traps using Owens Corning 703, the same material used in recording studios, sound labs, theaters, auditorioms, gymnasiums, sound chambers, you get the idea...
Also, this was when I only had ONE sub, the EP500.