Hi,
I replaced my double bass with an Aria SWB-04 thinking it would save space, silent practice etc. I sold it on after about 6 months. It was great, but mine didn't have the support bracket so it was almost impossible to play due to the bass spinning away and falling over and having to hold on to it with my left hand whilst playing. I would imagine, with the support bracket, it would actually have been really easy to play, action was very low for example.
Sound wise, I think the resonant chamber didn't really add all that much to be honest. The sound was quite hollow, probably more like a hollow body electric bass like a Jack Cassidy than like a double bass. It added that little extra bit of texture to the pickup sound when blended in so it sounded a bit less like a fretless bass but didn't make a massive difference. I've owned cheap acoustic bass guitars that sound more double bass-like, for example.
I also found the signal from the bass to be quite weak, I had to crank up my preamp pretty loud to be able to play through headphones and there's quite a bit of hiss form the elctrical system on these basses which can be another problem.
Hope that's helpful info?