We used Opus for one of our shorts here at REACHRIGHT. If you want to see how it came out, here's the link. ru-vid.comiOQkpDv91Lk We'd love to hear what you think of it.
Just tried this and I thought it worked really well. Video quality wasn't great, but I zoomed in from our wider camera shot to eliminate some background. The selection of clips was really good. I may try it paid for a month and see if it's worth it. I don't have the time to do it on my own!
You could always just put the audio with a blank video clip and see what happens. Then download and rip the audio back off the video so you have your audio clip. In theory at least.