I am a brand-new SMS-1 owner all of two days.
My first method of setting up my subwoofer was to put it somewhere in the room and play with the knobs until it "sounded good". Problem of this method is that I have to be able to distinguish the sub from my speakers, which is undesirable IMHO. The only objective measurement I ever did was SPL meter readings which I did not trust at all.
After about a year of using my sub in this manner, and building a new home theatre , I tried some measuring software (RoomEQWizard) and confirmed that my subwoofer was set too loud and my crossover (on the sub) set at the wrong point. I did some knob-tweaking-sort-of equalization and really liked the results. However, despite considerable room treatment and tweaking, my sub was still a little wild at certain frequencies. To do more I needed equalization.

After the first quick setup with the SMS-1, the difference was apparent, but not dramatic yet. Today I spent about 2 hours doing the manual adjustments and moving my sub around. I still don't think I have the best possible curve, but I am happy with it.

The best way I can describe the result is that before the SMS-1 I could hear my sub and now I can hear the bass.

The kids decided they wanted to watch Spiderman 2 and I turned up the volume on the 990 to a previously-unbearable -10dB (think cineplex bass boom) and I realized after having seen this movie again for the first time that there IS a soundtrack under all that sound. So that was dramatic and even more so (not sure why) was listening to SACDs.

IMHO, the SMS-1 is money well worth it. I have spent a lot of money on equipment, speakers, and interconnects, not to mention thousands in sound treatment. Getting to hear the sum of all those components working in unison is, as a credit card commercial would say, priceless...