For a brief while as I was selling my Studio 20's off I used a pair of Atoms as the rear surrounds.
Honestly, for home theater, I can say I rarely noticed a sound difference in this application. They sound decent for $200 or whatever they cost now, and are voice matched to other Paradigm models. This just means the frequency response has similar characteristics. Not a perfect match, but close enough for rear duty.

As for how much they are used - I use mine for any DVD and TV source, regardless of whether it was encoded in 6.1/7.1 or not. The processing is quite convincing, and in my large room the gap behind me is filled much better. I hated not having the rear surrounds during my last upgrade. It in no way diminishes the other 5 channels, but really provides for a more enveloping sound field. I always advise people though to make sure they get the most out of 5.1 before uprading to 7.1. It may be worthwhile in many rooms to consider, but it's not the high on the benefit/dollar list. YMMV.