subwoofer suspended from ceiling?

I have an open trussed ceiling. I am thinking about suspending the subwoofer between two trusses. My question is as follows- will the quality of sound be negatively impacted if I move the subwoofer from the floor (concrete slab) to a suspended location up in the ceiling? Thanks for your help.
Powered subwoofers are not intended to be located anywhere but on the floor of the listening room for proper LFE production and extension. It would be an interesting experiment but as Elevick states, you'll lose a great deal of bass extension from the sub by doing this. If you do try it for the heck of it, let us all know how it sounds as compared to it located on the floor.
Not a good idea from a structural vibration point either.
I think within time you would be listeing to your roof, rafters and walls rather than the sub.
Post removed 
We've done a number of designs with soffit mounted subs. There are issues, vibration, making a very rigid mount, but if you can over come those it can work well. In most cases the floor is simplier, and it's what most people do, but it doesn't necessarily mean it's best.

The 1/2 between floor and ceiling as Eric points out can sound very good. It cancels out the height mode which is typically the dominant axial mode. We do this regularly in our designs
Committed is what you should be for doing.Save that suspension for monitors or turntable on rigid pole.But Put this up so I can easily follow what happens.I am thinking of that scene in Young Frankenstein when they have to crank the table up to get the lightning.
I have suspended speakers for years. Suspension of subwoofers eliminates all kinds of floor vibrations for a start, and the speaker is decoupled from the structure of the room. I would definately give it a go, be careful as subs can be very heavy. You have to make sure the rope or threads (I have used very strong fishing line) can take the weight.
When I designed my custom SW systems which are embedded in a wall I located the two drivers, (for each of three SW systems) 15" and 12", stacked at the center of the Magneplanars, which is near halfway between floor and ceiling. Good results.
Sounds interesting. In my experiences and through reading, ear level and as close to the listening area as possible is my favorite sub position. My SVS Ultra 13 is on a table 8 feet from the listening position.

I feel subs are truely directional. Placing them on the floor is easy and may work best in some environments.

I've always had the best long term calibration and subjective results placing them at ear level near the listening positions.

If up higher is the goal, consider replacing the rubber feet with strong wood screw hooks and nice looking chains. The height can be adjusted easily.

consider trying a table just behind or to the side of your listening position. It's very clear, musical and viserally engulfing. As an added benefit, it's in a convenient position that's easily adjustable for the differences in classical to rock to HT. All I do is adjust gain.

Wow - comments from 2009 I wonder if anyone will see this comment in this Nov 2019

November 2022. I'm sure this thread will continue to be relevant for a long time.

As long as downstairs neighbors keep hating music at least.