So how many people are using subwoofers

If your goal is to hear it all kinda crazy not to. 

I have been running different bookshelf size mains with a sub for many years.  My room has a nasty peak at 40 Hz so it was always tough to get good sound with floorstanding speakers.   

My current system is a pair of Revel M106 speakers paired with a REL R305 sub.  I run the mains full range and drive the sub via a Velodyne SMS 1 which serves as the low pass crossover and allows me to tame the room mode.   The sub is crossed over low with a steep crossover, it'seems just the right amount of low frequency given the decent bass from my mains.

I'm driving the system with a Conrad Johnson Classic 2SE preamp and a pair of Quicksilver Mid Mono amps running KT66 power tubes.   My main source is a NAD M51 DAC fed by an OPPO 103d universal player.

For me a three piece system works best.  Friends and family are always impressed at the performance of such a small set of speakers. 

I'm using Golden Ear Triton One's. The sub is built in and can go to 16Hz. Sean, I think this qualifies as an exception in the case of vented. Dennisj, besides my T1s I know there are other high-end speaker manufacturers that use powered woofers of some kind. Not sure what you believe they are messing up but I do agree there can be an audible difference between a powered sub and non powered.

" I recently got Vandersteen 5 speakers that have true built in subs that go to 22 HZ, are very tunable, and have built in 400 wpc amps to drive the subs. I have never heard such great bass, and I love them. But a friend uses REL subs with MG 3.6s very successfully. I think Karls (above) gives good advice. "

Yeah, my Vandersteen 4As are 3 db down at 24 hz and I really don't think they need any bass reinforcement!  My main system speakers roll off at 20 hz, so same thing - BUT I do have a pair of Hsu VTF-15H subs to use only for home theatre use.

I have a friend that sets if home theatres and he says he's never seen any client that doesn't crank the subs up too high - meaning higher than the program material and higher than he set them up using very expensive test gear.

A proper sub used for listening to music should 1 - take the weight off the lowest octave for main speakers that are troubled in that area, and 2 - make their presence felt not as the all to common boom, but subtly as a sense of filling in something you hadn't realized you were missing before you put the sub in the system.

I've also used Vandersteen subs and found them to be excellent value and second their recommendation above.

Subs are good...the more the merrier.  They take the power required for lows away from your amp and regular speaker so that they operate better, cleaner, etc.